to be fair I've never downloaded the offline versions before because for years now Avast has been trouble free, I've barely ever thought about it
it only went sideways this year
however, some good news to report, the very very newest 20.9 beta, not the one from last week but build 5730, finally seems to solve the shutdown problem, it's now back to seconds instead of many minutes
but predictable, unfortunately, there is a new problem with 20.9, any GUI popup or attempt to bring up the menu immediately freezes the GUI and access to the rest of windows desktop until I use control-alt-delete to start the task manager
I'll use the 20.9 beta thread for that problem though, I guess technically this one is "solved"
ps. spoke too soon, had another 5+ minute shutdown earlier today on 20.9