SOLVED: Jellyfin Media Player Linux never shows subtitles

[Host-in-the-Shell]

It should be http://<your device local lan ip>:8096. Unfortunately, that number is going to depend on what your router has assigned to it. It's also a good idea to go into your router settings and assign a static IP to your machine hosting Jellyfin, so it's always on the same address locally. Doing that is also something that is going to depend on your specific router.

As for the config files, I'm not sure how compatible across these formats they are, but might be better to start fresh to avoid any issues just in case. There's really no way around the fact that both Arch (particularly base Arch) and Jellyfin do require some degree of familiarity with certain things such as system administration and system services management; you don't have to be an expert, but will have to dive a bit deep through a lot of documentation, particularly in terms of administration post install. EndeavourOS only facilitates the installation process with a graphical installer and does introduce some out of the box system management beyond what vanilla Arch does, but outside of that, you will need to learn how to administer, configure and troubleshoot your system; in other words, read through the archwiki a lot. This is why I prefer base Arch, since it doesn't abstract the installation process and prepares you for Arch's more hands on system administration model.