What devices are missing support in your case? Not an exhaustive list of clients

Can cast fairly well from the phone app or even the browser. Chrome cast is funky though.

Enabling internet access is also a huge pain unless you're willing to raw dog the entire internet.

Also even common stuff like Chromecast-ing will randomly break on Jellyfin and nobody can explain why.

What "stuff" are you referring to? Has the webapp, Android, iOS, Firesticks, Roku. What are you trying to run it on? Even my SmartTV has it in thier native store.

I'm gonna guess plugging in a roku is too much for them, too? When Arthur C Clarke said his magic quote I didn't expect that line to be drawn at shiny lights on a screen for most people.