Yeah, I agree, though making software that can run in a distributed configuration is a matter of following a few basic principles, and would be far less work than what the developers have spent chasing down trying to make SQLite work for their application.
The effort required to put an application on Kubernetes is a pretty good indicator of software quality. In other words, I can have a pretty good idea about how difficult a software is to maintain in a single-instance configuration by trying to port it to Kubernetes.
Most of the issues with the database are old sins from Emby. With 10.11 the Jellyfin team finally managed to clean up that mess so they can move forward with a clean implementation. Their blog post on moving to EFCore [1] and version 10.11 release post [2] have more details.
[1] https://jellyfin.org/posts/efcore-refactoring [2] https://jellyfin.org/posts/jellyfin-release-10.11.0/