Hi all, I can now announce that the one-click update from my hosting panel worked as I thought! With the old setup, if I'd had the right permissions, I would have had to download and upload files manually. Very much something I didn't want to do, and also that nobody should have to do in 2022. Now when the forum is installed using a one-click installer, it can also be updated that way and I'm very happy about that.
We are now updated to version 3.3.7. Apparently, I missed the 3.3.6 version, which was no loss because it had a weird issue with user permission.
However, updating with the one-click tool seems to remove all custom theme files!! I came to a horrible white page and thought something was seriously wrong, but found the error and could use the theme files from the backup.
Very annoying but at least now I know it for the next time.