Some months ago I installed Ubuntu Mate 22.04 on my old(ish) Dell laptop. Internet worked fine - I was using both ethernet and wifi. Yesterday both ethernet and wifi stopped working. I rebooted the laptop, I rebooted the router. Nothing helped. Other computers connected to the network, have no problem with internet connectivity. I booted the problematic laptop into Windows (it's a dual boot, but I hardly ever use Windows) and the internet worked just fine. I booted the laptop into Ubuntu Mate 2022.04 from a USB and the internet works just fine (I'm actually writing this from there).
I am able to connect to my lan. It's just the internet that's not working.
So what's wrong? Where do I begin to fix this hugely frustrating problem?
Any and all help will be highly appreciated.