What new device should I buy that direct play's AV1 content?

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This is a tough request, if I understand correctly, because you're asking for something that supports AV1 decoding (i.e., playback) as well as pretty much every other video and audio codec, plus will play back ASS and PGS subs without transcoding? You might be looking for a unicorn, friend. Playback with PGS subs without transcoding limits your selection to devices generally with custom players, as Roku, webOS, and most other players I'm aware of will NOT support PGS playback without being burned in. Add to that older codecs being dropped, H264 high being a problem for folks who watch older anime, audio channels, Atmos, HDR/DV/profile...

If you're satisfied with 80-90% of that, you could probably find a consumer device that satisfies your needs, but you're cutting it close to finding/building HTPC hardware and running a custom-built OS designed for this purpose to fit your needs. That's gonna be double or more the cost of a consumer device plus the time investment and maintenance...