In these cases I'll do the same thing other people here seem to do as well. Do a backup (or snapshot) and then I'll try to just do it. Obviously read the documentation on updates and major version upgrades first. I think that's fine in the case of paperless-ngx.

Either it works or it doesn't. In that case I'll gather error logs and information for debugging and roll back to the backup. After a successful major upgrade, I often go through the settings and config and check about all the things that have been added or changed in the meantime and make sure they're set to my liking.