I have the similar issue on 6.10.460.1 build - YouTube is not playing videos on one laptop (never-ending spinning wheel on ANY video). The only solution which helped me so far is to disconnect ESET Network Protection Proxy from Network Settings and then video starts playing (Proxy automatically reconnects immediately back).
This happens on only one laptop - others don't have such issue (although, they running 6.10.400.1 build, not sure, whether it is caused by the latest ESET build). MacOS version is Big Sur on all of them.