Jellyfin is a fork of Emby. Emby used to be open source, when it went closed source Jellyfin was formed off of it.
AV1 playback works on devices that support it. You'll need server-side transcoding for devices that don't. Jellyfin can do this by shelling out to FFMPEG, which can optionally use hardware accelerated codecs if they're available to it. So basically, "it depends", but Jellyfin itself supports AV1 media.
AV1 playback works on devices that support it. You'll need server-side transcoding for devices that don't. Jellyfin can do this by shelling out to FFMPEG, which can optionally use hardware accelerated codecs if they're available to it. So basically, "it depends", but Jellyfin itself supports AV1 media.