This all feels like it should be 800x less of an issue because phones & tablets should just be able to connect over SMB & you should use whatever media player you want on your device. Telling your home router to forward 445 is not that hard. Usinf minupnpc or just building in auto-port forwarding would be better. Alas I've seen some isp's block users from connecting to 445, which seems insane (my ispets me host there…
And as someone who used to watch over SSHFS for years... the biggest feature of things like Jellyfin/Plex is automatically remembering what I'm watching and where I am. Admittedly it's mostly an issue if you watch shows instead of movies (I'm never going to remember which episode of 52 episodes I'm on) but having the app remember is so much better than updating a wiki page/text file/whatever manually as to where I am so I know where to restart watching (which I've accidentally messed up before. Very fun to watch stuff out of order and be like "wut....").
Speaking of dlna... it's kind of awful (at least years ago when I tried to use minidlna with my TV). It's way better to just get a Linux mini PC and hook that up to the TV and let the TV be a monitor.
(Also yeah, I wish we had a better than Android option for phones... https://puri.sm/products/librem-5/ exists if you want to throw a bunch of money at it, not sure if there's a whole lot better)