Just wanted to post this in case others run into the same issue:
I upgraded my laptop (Lenovo Thinkpad X1 Yoga 5th Gen) from Win10 Enterprise to Win11 Enterprise, with Avast Business (multi-tenant) AntiVirus Pro Plus installed managed by a policy that turns off Avast Firewall but doesn’t disable it - after upgrade completed, both WiFi and wired network that I connected to were showing Public and I could not change them to Private via PowerShell or Win11 Settings - they just reverted right back to Public. Tried enabling Avast Firewall but I couldn’t click to “Trust” the network in the Avast Firewall component interface on my PC. Ended up removing Avast entirely and I could then change the network to Private, and then reinstalled and so far “Private” network is sticking.