After installing the HEVC Video Extensions from the Microsoft Store in Windows, it enables HEVC support in Edge Chromium, and Netflix can even play HEVC streams (in HDR, no less) through the browser once this is done. Plex Web however, cannot do HEVC Direct Play in this browser for some reason. Please enable this.
There’s an existing feature suggestion addressing this topic.
Please vote/comment in that thread in order to avoid distracting/dispersing votes.
Therefore closing this thread as a duplicate.
2021 clean-up: duplicate