Theoretically, support for that could be coming... Emby (where Jellyfin is based on) always used their own layer for interacting with a SQLite database. All that custom made logic is currently being swapped out for EF Core. EF Core is a DotNet library for interacting with databases and EFCore that also supports MySQL, PostgreSQL, SQL Server besides SQLite.
So my guess is that, once all that work is completed, support of other database can be added.
For a little bit of context. I am currently running Jellyfin on Btrfs and there is quite a performance impact due to CoW. If 2 clients decide to browse the libraries, both clients grind to a near standstill with regards to being able to see things. So I am following this work with quite some interest.