Netflix reported in 2025 something like 30% of traffic was av1. I think smartphone and PC support are fairly robust but under the impression streaming devices are still quite terrible unless it's a Chromecast.

AVC/h.264 is the only thing I know of that's pretty much universally supported at this point. I found a Facebook/Meta report citing some consultant provided data that VP9 was a close second. Limiting to devices from the last few years, HEVC might work.