I typically use Chrome. So far I haven't been able to get GPU video decoding to work with it. Today I tried the default Firefox version, the one that ships as a snap, and GPU video decoding, appears to just work. It was a bit shocking. I have an 11th gen Intel Framework.
Here's how Chrome looks on the same video at the same 4K setting:
Pretty sure Framework had nothing to do with it. They have no mechanism to change software or drivers in Ubuntu / Firefox. Mozilla and Canonical do.