It is not only Avast free version, also Avast Premium Security for Mac does not work anymore. Concretely, 19 of the VPN proxies and the proxies for mail and web. Mail can't be collected with Avast Email Shield enabled, and the Avast Webshield seems to be behind frequent disconnects.
Yes, I tried reinstalling the newly downloaded Avast version. No, it did not fix the issue.
Have I tried to switch it off and on again? You bet I did. Brings temporary relief, but the issue reemerges.
Did I report to support? Yes, I did, Avast Support would not even acknowledge receipt of the issue, completely unresponsive.
3 year license, just bought in March and now I need to uninstall Avast, so that I can work properly.
Perhaps Big Surwas too much of a surprise for Avast.