I have a 2015 Dell XPS 13 (9343) with Ubuntu 16.04. Wifi is working using bcmwl-kernel-source 18.104.22.168+bdcom-0ubuntu8 and everything works fine except that I cannot see all wifi networks around, in particular the one I want to connect to.
Using an old TP-LINK usb dongle I can connect normally.
I think the problem can be the router mixing up the b/g/n and ac/a/n fequencies.
Strange thing is that while I was using Ubuntu 14.04 everything worked fine.
Any suggestion about how to solve this issue?