Do you need UDP? I see lots of multiplayer browser games. Here's a few
Google shows me a bunch of RPGs
https://www.google.com/search?q=browser+based+rpg
FPSes here
or maybe better a video showing some
https://www.youtube.com/watch?v=9ad5jcXPbNw
I know none of them are Edlin Ring, Skyrim, or Call of Duty. One issue with Web games is users's expect them to start quickly so no downloading 80gig of assets like 102gig for CoD Black Ops 6