Android: "Connected without internet"

My phone (Samsung A42 5G) does not get an internet connection through my router. Other devices on the network are fine; just the dang phone is a problem. I get "Connected without internet" when returning home to use wifi. This may last for minutes or hours before something mysterious decides to let me access the internet through my phone. It persists through multiple reboots of both the phone and the router until connectivity is mysteriously restored. The router shows the phone is connected, but I get no internet access. Once I have access, if I go out of range and return, it's back to "Connected without internet."

What's up with that?