By quitting he is potentially allowing the administration to fill the position with a trump approved “yes man”. I think he could do more good by keeping his position and defy/resist orders instead. I don’t blame him, though. Getting the hell out of there seems reasonable too!
I did this about a month ago and also had some challenges. I’m not an expert and my understanding is not good enough to troubleshoot your error messages fully, but it does say the header size is not matching the expected value. I have my Jellyfin in Docker compose on a OMV VM running in Proxmox and passed through an arc a310, so very similar. I used “Device: - /dev/dri/:/dev/dri/”, that worked fine and “renderD128” can be chosen in the Jellyfin device drop down menu. The biggest issue I had was the render group not being imported correctly into the container. So even though I added my Docker user to the render group in the Docker compose .yml, the group got a random garbage name inside the container so it didn’t match. Not the expected group “render”, but something like “video73628ds”. Ended up making a custom Jellyfin Docker compose image that has just two lines "FROM Linuxserver.io.jellyfin:latest " (I think), then a line to import the render group from the host to the container (don’t remember the command, writing this on my phone). Then I built that image and used the built image in the Docker compose .yml instead of the normal linuxserver.io image.
Freetube has integrated sponsor block (might have to enable it in the settings first). I’ve generally been very happy with the Freetube flatpak, although there have been times when YouTube actively fought against third parties where Freetube did not work for a month.