I’ve poked around online and it seems like Jellyfin had (music) volume normalization added to it sometime recently. However, I’m struggling to verify that it’s enabled/working. Is it something I have to enable or is it on by default? If it’s on shouldn’t I be able to see something like a LUFS or ReplyGain value in each song’s metadata?
UPDATE:
I’m not familiar with Jellyfin’s git strategy, but it seems like even though the audio normalization has made it into the master branch it has NOT made it into the 10.8.z release tag/branch. I determined this by looking for the changes in Emby.Server.Implementations/Data/SqliteItemRepository.cs from the normalization PR in the current version of the file in 10.8.z and they were not present.
It’s specific to music, per the OP. As far as boosting the volume goes, it varies based on your client and devices, but on many TVs, sound bars, and AVRs, you can enable “Night Mode” and it’ll turn on a compressor that basically makes all content played on said device sound closer together in volume (so less of a dramatic swing between Jellyfin volume and other stuff)