Since quite a while I was running a Pi-Hole DNS server in my network to block ad- & tracking requests for all devices in the network (more info about Pi-hole are on Wikipedia).
All was great until at some time our Android devices suddenly couldn’t connect to the WiFi anymore. They reported “Connected, No Internet“. All other devices, connected via LAN or WiFi were just fine: PCs, FireTV Stick, other PIs – no issues. When I disabled the use of PiHole, they were able to connect again.
After a while I realized that this could be a common problem which seemed to appear after some upgrade. Unfortunately, I can’t remember if I updated at all. I also didn’t check the logs (which I should have done) for any warning.
The solution that worked was to permit DNSMASQ_LISTENING an all origins in the network settings:
“Settings/DNS/Interface Settings” > “Permit all origins“.
As soon as I switched the setting, suddenly everything worked like a charm.