A few months ago I bought a second hand Nvidia Shield TV (€40), flashed LineageOS on it. Very happy with the device, especially the performance.
I use Jellyfin, SmartTubeNext and some VOD TV apps from my country. I've Adguard Home on my Proxmox server (can also be a Raspberry Pi) that I use for DNS adblocking, so we can watch VOD TV without any ads. Works really well :)
We've switched to this from cable TV and my family loves it, we can watch anything we want without any ads and FREE!
Only problem (not for me) is that Netflix doesn't work on it without GAPPS.
+1 for the Nvidia Shield and LineageOS route. Keep in mind that LineageOS doesn't work with some proprietary features on the box such as:
Dolby Vision
AI Upscaling
Although this hasn't really bothered me. This solution is basically set and forget. Is stable enough to leave at my parents house with almost no complaints.
Also another weird usecase... I use these nvidia shields for my LAN parties as thin clients.
I believe DV HDR is being downgraded to HDR10+. I can't really tell the difference though. I still get the little 'HDR' logo when I try to play a DV HDR movie.