I've got a Dell AIO 5488 (nice system with touchscreen) which I've decided to start using for some things, but having unusual network issue.

This used to be at one of my employers offices, and used every day with Windows 10, and had zero issues. Upgraded that office a few months ago and I took the Dell home.

I installed Linux Mint on it initially, and worked fine. Then didn't touch the system again until this weekend. It would not connect to the internet, via cable or wifi - it said it was on a network but no traffic.

So I reinstalled the OS - initially got full internet, then the browser stopped working. But the updater software etc worked fine and could talk to my home server.

Installed Windows. Same issue, could get Windows Updates, but browser failed to load anything. Noticed it was getting a 169.x.x.x address - but how was it getting the updates in that case.....  tried manually setting IP etc. No change. 

Installed Ubuntu. Same issue AGAIN. I can download updates etc, but NO browsing, and cannot access anything else on my network.

I've checked the router (Fritz) for anything unusual and cant see any issues there (rebooted it anyway).

The only thing "wrong" that I've found, is that the CMOS battery needs replacing. But I've never experienced this sort of issue before with a dead CMOS battery.....  anyone else ?

I'll replace the battery if I can find one in my stores, but in meantime, any other ideas ? If battery does not work, I'll factory reset the router and see if that helps....