PHP 8.0 works with nextcloud 24 and as you experienced it also worked with nextcloud 25. So that’s unlikely the problem.
I could be wrong on some points but things could have gone (more or less) in this way:
The web updater replaced nextcloud installation files, probably modified something about the database (like something that is checked during upgrade and one of the things preventing the downgrade, unsure about that), and also some parameters in the config file (version…)
To keep it short and disregarding some steps, the rpm update replaced nextcloud files, probably didn’t modify the database as it was stopped by the nextcloud error, and maybe changed the version in the config file. Other things (php and mariadb versions) were already the same and should make no difference.
So you now have:
- nextcloud 24 files
- nextcloud 25 database
- nextcloud 24/25? config file
And need, at least, to “upgrade” the nextcloud 24 files to nextcloud 25.
Before messing with this, make a copy
/usr/share/nextcloud (so with that you preserve config file, config folder, data folder, and apps folder). Then follow nextcloud upgrade guide adapting it to nethserver paths.
Have backups (and snapshots depending on what you use)
Some excerpts from the docs:
- Manually upgrading is also an option for users on shared hosting; download and unpack the Nextcloud tarball to your PC. Delete your existing Nextcloud files, except
config/ files, on your hosting account. Then transfer the new Nextcloud files to your hosting account, again preserving your existing
Manually upgrading with the Nextcloud
Downgrading is discouraged by nextcloud:
Downgrading is not supported and risks corrupting your data! If you want to revert to an older Nextcloud version, make a new, fresh installation and then restore your data from backup. Before doing this, file a support ticket (if you have paid support) or ask for help in the Nextcloud forums to see if your issue can be resolved without downgrading.
Replacing version on config file could trick occ and let it run through but with old install files and more recent database from different nextcloud major version results are unpredicted.