I'm eagerly awaiting the final release of 1.6, but because my host is going to start charging a fee this month if I don't get off of PHP 7.x, to avoid closing down my site, I may have to upgrade to the most recent release candidate in the meantime.

Since upgrading to PHP 8.x breaks Zenphoto 1.59, I wondered the best method of updating... My plan would be to do the following:

1: Backup my database for safety via Zenphoto
2: On my host, change my PHP from 7.4 to 8.1 fast CGI (or will this release only be for 8.0 at this time - I can choose from 8.0 CGI, 8.0 FastCGI, 8.1 CGI and 8.1 FastCGI - which do you recommend?)
3: Via FTP, delete the zpCore folder and my themes folder (except for zpBootstrap, which I use, and believe will work with some tweaks I've worked out in another thread - the test will be an install with more than 2 pictures, lol).
4: Upload index.php, and the zpCore folder and theme folder from the new release, replacing what I just deleted.
5: Log in and follow any instructions given.

If this is incorrect, let me know, please. Thanks, and thanks for all your work in preparing the next release!

I guess I know which host you are on if they charge extra for older PHP versions…

The update procedure is still the same and described here: https://www.zenphoto.org/news/installation-and-upgrading/
So your's is generally right except that you already should be logged in for the upgrade.

As for PHP I suggest to generally use FastCGI. Zenphoto 1.6 will be PHP 7.x to 8.1 compatible - 8.1. is part of causing the delay - and probably even with PHP 8.2 to be released later this month (unless their docs didn't tell everything).

You can already test the pre version from the current master aka 1.6RC:
https://github.com/zenphoto/zenphoto/archive/refs/heads/master.zip

There might be some more fixes over the next days but that is basically the release. Note this is a bigger update so a few things changed under the hood that a 3rd party theme like zpBootstrap may be affected by besides PHP 8+ issues.