I just can't recommend anything with Android anymore. The enshittification is real. They're already rolling out full-screen video ads in the OS. Even Plex lived long enough to become the villain.
I've just been plugging in my laptop. Super inconvenient but that's where we are now.
I'm back to a full computer again too, and if you don't have a laptop handy, the new little mini PCs are surprisingly affordable too. If you don't want to build a raspberry pi.
RPi's probably not a great option anyway. Too low-powered for streaming video.
I'd probably recommend one of the used USFF office PCs w/ X86 processors commonly for sale on eBay for cheap. Bonus: These are the same ones people will recommend for low power homeservers so you could have it running those as well.
What about a chromebox flashed with some linux os? Nice and cheap mini x86 pc. Just picked one up for 35 bucks with an i7 6th gen, just hoping it uses sodimm and isnt integrated on the mobo.