Try resetting your Firefox profile. Sometimes a weird setting can break browsers in spectacular ways.
This was a big one for me, for the longest time I could not figure out why I couldn’t get YouTube to play videos over 1080p for me in Firefox on my PC, it ended up being some weird setting that I changed in about:config
(I sadly cannot recall which one) a long time ago - but I’d always copied my Firefox profile with me so that bad setting stuck around.
A lot of Rocket League! Additionally I’ve been having a pretty good time with Star Trucker.
Then recently I’ve been streaming Helldivers 2 from my PC to my Deck while it’s connected to the living room TV, which has been fun.