Problem just recently showed up. When I switch the SD card with another Rpi-4, the problem follows the SD card, and the other Rpi-4 can access the inter-tubes using Raspberry Pi OS.

Stellarmate OS seems to be working well in every other way. I am able to SSH and VNC into the Rpi-4 on my home network. Stellarmate OS connects well to my home network, and the Hotspot worked during initial startup. However, if I try to connect in any way outside my home network it just times out. Even the "http://localhost:3000/#/home" address in the Chrome browser times out.

I've rebooted the network controller, and the Network Setting on the Pi show the correct DNS address (192.168.1.1)

Any suggestions?

OK, problem fixed. I was using an additional button WiFi dongle to connect to my mount wifi - which acts as an access point router. Stellarmate OS was looking there for inter-tubes. I unplugged the button WiFi dongle, rebooted, then plugged the button dongle back in. All fixed.