I found, meanwhile, that uninstalling any of the recent PowerToys version in 20H2 does ease - not entirely remove - the issue and makes 20H2 working quite well.
It seems that the integration of PowerToys with Windows Explorer does somehow add to the freezing. After uninstalling, at least with my machine, I found around 70% less freezing per hour (incident count went down from 10 to around 3 times).