I'm having this problem on 1.16.5 when loading into worlds. I've tried restarting my computer, reinstalling Minecraft, and tried different worlds. Still having this problem when loading into worlds, single player, multiplayer and realms. Nothing seems to work. I'm using the newest Java version on Windows 10. Been having this problem for multiple days now. Game is completely unplayable and my realm subscription is being used up even though i cant use it, very annoying.
It was the Max Framerate for me as well. I'm not sure how your max framerate ended up at 0 but i'm quite sure that mine was due to me using different clients, one of them being Lunar Client where if you put the max framerate at the lowest possible it goes to Vsync mode. Thanks!