The bare minimum is to backup the Plex database files, com.plexapp.plugins.library.blobs.db and com.plexapp.plugins.library.db.
However, you should back up the entire Plex data folder and registry settings to protect from a catastrophic failure such as the drive failing and you cannot access any data.
To restore: Move an Install to Another System (you’re effectively doing the same thing).
I run PMS on Linux, not Windows. I’ve edited the registry on my Win10 PC, but have no experience with backup or restore procedures.
The Backing Up Plex Media Server Data document has a link to a Microsoft article regarding backing up the registry.
I checked the Tips & Tricks section of the forum and found PSA: Script to back up and restore Plex app data on a Windows system. It was updated in April, so the author is keeping it current. You might reach out to him regarding support for Windows 11.
FYI, the registry entries contain the server identity and settings, not any info about content, collections, etc. If you do not have the registry info, you can still restore the server, since that info is in the Plex data folder. You will have to re-claim the server and re-share libraries with any users (just re-share, not re-invite).
