Removable drive management

[Efficient_Good_5784]

You can also have Jellyfin write NFOs and make them read only to preserve metadata.

Actually this seems to be the best way! Could you point me to a guide to do so, please?
This wouldn't prevent me to have to rescan library though, right?

You'll have to write a script or cron job that does this for you. It's a simple enough task.
If your server is on Linux, just have a script periodically chmod the nfo files in a directory to only allow the Jellyfin user to read them only.

Basically a "chmod 440" applied to the nfo files if you want to make owner & group all have read-only access.