I was already thinking of upgrading my old Roku to a $20 Onn (Walmart brand) Google TV box (which I'm told is hackable), but this will only accelerate that decision.
No need for HTPC, just a small USB device with HDMI output and DLNA support. You use your phone as a DLNA controller, a server running Jellyfin as DLNA provider, and the device attached to the TV as DLNA renderer. And sometimes TVs have DLNA support built-in (my Toshiba does).
On Android there's an amazing app called BubbleUPnP that can source media from a wide variety of places, make playlists, and cast to DLNA devices as well as proprietary protocols like Chromecast.
Jellyfin supports DLNA too, if you have a DLNA rendering device on the network it will just appear in the cast menu. Or if you want something that works with a remote directly on the TV you can install Kodi. There's really no point nowadays in getting tied up into proprietary stuff.