Unless you absolutely need a new OS version, there's no reason to even move to a new provider. Regarding the VPS, well, that doesn't surprise me. But with most providers they give you many versions of Linux to choose from. The way Linux typically works is a lot of the software repositories (where you download software from) are kinda locked to specific major versions of software. So if you want updates, you have to upgrade the entire OS to a new version. However, these operating system maintainers have guaranteed EOL dates, and will support all the software until the specified date (though there's no guarantee some third party software you're using, like WordPress won't need a more updated version). There are some tricks around this, such as using 3rd party sources for updated software packages or delving into the realm of containerization. But anyway, unless you need a specific version of PHP for some feature (or to meet the requirements to run WP at all), it's not something that's that important. I will also say that usually a VPS is completely unmanaged and you as a customer are expected to handle all aspects of it, though not always.

Though I'm not entirely ignorant about servers, as you can tell, my experience isn't anywhere nearly as great as yours, so pardon me if this is an obvious question.

Your statement makes it sound a little as if OS updates are relatively trivial. I was kind of assuming they were a bigger deal than that. And it irked me that BH updated me from CENTOS 6 to 7 when 8 was already available. By the way, BH didn't notify me of the impending CENTOS 6 end of life. I had to ask support about it, and the tech was happy to schedule it, but if I hadn't said something, I'm not sure when (or if) it would have happened. That goes along with your last statement about VPS being unmanaged.

Anyway, that is kind of why I switched to Cloud Linux (which seems like a stupid thing to have done, though at the time it made sens). That's particularly true because it looked at the time as if CENTOS was going away in favor of something called CENTOS Stream. For example,

CentOS Linux 8 will reach end-of-life on December 31, 2021. No further updates will be available after that. The moment a security update comes out in 2022, you are at risk with CentOS Linux 8 from that point on.

You should absolutely have migrated well before this date to something else.

Some candidates for CentOS Linux 8 alternatives include:

* CentOS Stream
* RHEL (no-cost subscriptions)
* Alma Linux
* Rocky Linux
* Springdale Linux (formerly PUIAS)
* Oracle Linux

https://forums.centos.org/viewtopic.php?t=78026
And I said to myself, oh, that's why BH didn't update me to CENTOS 8, because it's going away. (Even CENTOS Stream is being replaced by Red Hat Enterprise Linux, though I didn't hear about this at the time.

This and several other posts I read during the time period gave me the impression that the various Linux varieties were more or less interchangeable. (And indeed, though I've now found a false statement buried on the BH website about updates to other Linux distributions being incompatible with BH hosted sites, BH didn't really seem to address the question) Not anticipating the bind that I'm now in, switching OS made sense, and CL had a script specifically designed for it, which did indeed get the job done.

Anyway, here are my options:
Try to revert to CENTOS 7 and let BH update to whatever its next preference is. There may be risks to reverting. There was a script at the time, but the site has changed a lot since then, so who knows? Also, BH takes a long time doing this sort of thing. It's not as fast as I could do on my own--if there were no issues.

Try to update CL 7 to CL 8. As Matthew has noted, that can be risky.

Dump the whole thing and just use Substack. Though it has a lot of features, it's too soon for me to make that radical a change. I see it as a supplement rather than a replacement (though since it's free, it would be an incredible savings).

Switch providers. Honestly, the only downside there is losing about a year's worth of hosting I've already paid for.

I've looked at Siteground, which, as RC suggests, has a fine reputation. I've also looked at A2 Hosting, which I'm leaning toward. It uses both cpanel and Cloud Linux, so the transition would be slightly more seamless than with Siteground. The Cloudflare integrartion also seems a little more straightforward. But what really draws my eye is that A2 
offers Managed VPS. (BH seems to have managed plans only with shared hosting, which is much slower.) Though A2 also allows clients to have root access (which is handy on occasion), the managed ecosystem would completely avoid the problem I'm having now. Also, A2's managed VPS is cheaper than comparable unmanaged VPS on BH, even ignoring the new customer discount. A switch now would lose money in the short-term, but in the long-term, I'd be saving.

Anyway, I have a little more time to contemplate. I'm planning on arranging things so that everything I need in May is offsite, just in case. A2 and Siteground both offer free migration, which should be smooth, but in case there's a glitch, I'll avoid a lot of unexpected end user downtime.

Thanks for all the help!
 

Wouldn't turning off any automated updates on cpanel resolve the issue until BlueHost updates to CENTOS 8?  Unless cpanel is a subscription now, if they drop support for older OSes on June 30th, that should mean they are just not going to be releasing any updates for it.  The current version should continue to run until BH updates to CENTOS 8 or until you update Cloud Linux 7 to whatever.

Here's the message:

cPanel & WHM version 110 will be the last version that supports CloudLinux� 7. Support for version 110 will end June 30, 2024. We encourage you to migrate to a server running AlmaLinux 8, Rocky Linux 8, or CloudLinux� 8 before June 30, 2024.

In other words, I turned off updates for cpanel months ago. (The current version is 118.0.4.) Cpanel provided a channel for updates to 110, which I have frequently received. But that channel now seems to be gone, and instead I'm told update to 118.0.4 has been blocked (from my end). In other words, June 30 is the end of the runway, period. We've already had the continuation of the old version for as long as we're going to get it.

Just wanted to further address some things

Second, well that's a good question. Bluehost seems to sit on old OS software for as long as they possible can. Their documentation still refers to CENTOS 7 when the current version is 8.5. And CENTOS 7 also loses cpanel support on June 30, but there's no reference to that in any Bluehost document. There is an unofficial update for an inplace  upgrade, but it looks just as fraught as the CL update. So even if I downgraded from CL to CENTOS (which might be marginally less fraught), I'd still be a little less than three months before end of life with no clear path forward. But at least that situation would be recognizable to Bluehost.

I still work in a software-adjacent job, and let me tell you that this is fairly normal. If you're using the Bluehost-recommended OS (CentOS 7), and they're managing the upgrades, they'll figure out how to migrate you to a new version themselves before the deadline. At my current job, we get notified of EOL (end of life) software 6 months out, and try to do all upgrades within 3 months, but we've had some with only a week to spare. Still, it shouldn't be your job as a customer to be worrying about this.

Also, the commonplace suggestion at the time (and still, for that matter) is to migrate to another server (!?). If you're a business with a large IT department, great. But someone like me is dependent on the hosting provider--unless I want to switch providers. I have no problem with Bluehost normal operations, but their support is a little...less than one might want. Switching from a lesser plan to VPS resulted in a downgrade of my PHP version (all the way down to one that was barely supported anymore). Easy fix, but still not something that should have happened. And support wouldn't have figured it out if I hadn't pointed it out to them.

Unless you absolutely need a new OS version, there's no reason to even move to a new provider. Regarding the VPS, well, that doesn't surprise me. But with most providers they give you many versions of Linux to choose from. The way Linux typically works is a lot of the software repositories (where you download software from) are kinda locked to specific major versions of software. So if you want updates, you have to upgrade the entire OS to a new version. However, these operating system maintainers have guaranteed EOL dates, and will support all the software until the specified date (though there's no guarantee some third party software you're using, like WordPress won't need a more updated version). There are some tricks around this, such as using 3rd party sources for updated software packages or delving into the realm of containerization. But anyway, unless you need a specific version of PHP for some feature (or to meet the requirements to run WP at all), it's not something that's that important. I will also say that usually a VPS is completely unmanaged and you as a customer are expected to handle all aspects of it, though not always.

Is this for a book that's text or mostly images?

If the latter, they might need to look at Comic Book Creator (or something like that) that Amazon has for creating comic books.  I don't know if it has an option for a square eBook, but I would think it would allow for square panels which might be a possible compromise.

A few questions for you:
What's the actual End Of Life dated listed for Cloud Linux 7? Can you postpone trying any OS updates until sometime after your launch?
Why did you switch to an unsupported operating system? Can you switch back to a supported operating system rather than just doing this upgrade?
Have you considered fully-managed hosting? There are tons of providers, especially for WordPress, so you don't even need to worry about these OS upgrades or system updates. These are usually more expensive, but one call to a contractor may be more expensive than a year of managed hosting. (If you don't like Bluehost, perhaps you could ask for a pro-rated refund. Looks like they also have cloud, managed WP hosting which you could maybe ask to be migrated to, paying a difference in price as needed)

For the first question, June 30, so yes, I could postpone. But really, my launch isn't that dependent on my website. And there is something to be said for getting the earliest start possible if there could be complications.

Second, well that's a good question. Bluehost seems to sit on old OS software for as long as they possible can. Their documentation still refers to CENTOS 7 when the current version is 8.5. And CENTOS 7 also loses cpanel support on June 30, but there's no reference to that in any Bluehost document. There is an unofficial update for an inplace  upgrade, but it looks just as fraught as the CL update. So even if I downgraded from CL to CENTOS (which might be marginally less fraught), I'd still be a little less than three months before end of life with no clear path forward. But at least that situation would be recognizable to Bluehost.

As I recall, I did the switch from CENTOS to CL thinking that I was getting CL 8, which would have gotten me out of the update box for a much longer time. The change from CENTOS 7 to CL 7 wasn't fraught at all, but it didn't get me where I wanted to be.

Also, the commonplace suggestion at the time (and still, for that matter) is to migrate to another server (!?). If you're a business with a large IT department, great. But someone like me is dependent on the hosting provider--unless I want to switch providers. I have no problem with Bluehost normal operations, but their support is a little...less than one might want. Switching from a lesser plan to VPS resulted in a downgrade of my PHP version (all the way down to one that was barely supported anymore). Easy fix, but still not something that should have happened. And support wouldn't have figured it out if I hadn't pointed it out to them.

I'm pretty sure there is no prorated refund, but maybe I actually would be better off shifting providers. That is a hassle in itself, but some of the better ones offer a free migration that might well be worth it.

Anyway, I have to go now, but thanks for the advice.