I just upgraded my Macbook Pro to MacOS 26 Tahoe, and after that I didn't have internet connection anymore. It was connected to the wi-fi, but couldn't reach the internet or my network.

In my case, this seemed to be caused by Little Snitch, which I had installed. I disabled it by removing it under Settings > Network > Filters (and I removed the program as well just to be sure), and after a reboot the internet was back.

I hope this helps anyone with the same issue.