Apologies on slow response, but it was in part to get the new v18.0 EspoCRM appliance published! It was a part of the latest batch of apps that we've built. I haven't actually officially announced it yet, but the new images are on the mirror and I've just updated the appliance pages so it can be downloaded (and actually now I think of it, it should have been available via Proxmox since yesterday).

So you have a few different options to upgrade but I'd recommend migrating your data to a new instance of the v18.0 appliance. Please note that v18.0 doesn't actually provide an easy way to upgrade to a newer PHP (yet) but as it comes with PHP 8.2, (and PHP 8.3 has only been out less that 2 months) it should be a while before you need to upgrade PHP again. And as always, with the Debian default PHP, you get the auto security updates (which the third party alternate PHP versions don't support).

You can migrate your data using TKLBAM (which requires a TurnKey Hub account. Run a backup on your current server, then restore to the new one. Note that by default, that will also migrate other config and files from your old server. If that isn't what you want, then you can limit the restore to just the EspoCRM files and DB like this:

tklbam-restore BACKUP_ID --limits="/var/www/espocrm mysql:espocrm"

(Where BACKUP_ID is the actual backup ID number - also please double check the paths/DB name, that should be right, but best to double check).

If you don't want to use TKLBAM, then EspoCRM provide a doc page on manual backup and restore, as well as another page on migrating to a new server. If you go this manual way, then before you restore your data on your new v18.0 appliance, I suggest clearing the existing (default) EspoCRM files (in /var/www/espocrm) and dropping the existing EspoCRM DB. You'll likely need to reset the espocrm DB user password too (and copy the new password into the espo config file).

Another option is doing a Debian "in place style upgrade" (i.e. upgrade the base OS)- see the official Debian upgrade docs for info. That should generally work smoothly, although there are a few details (such as you'll need to manually download the TurnKey Bookworm keys). It's also worth noting, that if you are using a TurnKey version older than v17.x, then you'll need to upgrade to each stable Debian release one, by one (in place Debian upgrades to not support skipping major versions). Technically speaking we don't support this option, but as I say, it should work fine and I'm more than happy to give my best effort support if you hit issues.

There are other paths you could go, but I couldn't recommend any of them, hence won't elaborate any more on that.

Hopefully that's enough to give you somethings to look into further. If you have more questions or hit any issues, please let me know and I'll do my best to help out.