Tl;dr: is there any way to do a fresh install on it so that everything (particularly the WiFi!) works right out of the box? My machine originally shipped with Windows and now has a hacked-together Ubuntu 18.04 running on it but I want to try a reinstall.

Full story: Hey guys, I'm just getting into Linux after waiting for it to mature so I can use it without too much of a learning curve. I bought the 7390 but, because I needed the 2TB and I'm in Canada, I could only get the Windows version. I did and I'm glad because it forced me to dive right into troubleshooting: installing Ubuntu 18.04 killed the WiFi. Which was especially tricky because the machine has no ethernet ports. I fixed that with a USB-C-ethernet adapter (turns out that not all work with Linux, that was a surprise; Best Buy didn't have any but both the ones I got from the Microsoft and Apple stores did the trick, fyi), but in doing so I had to hop back and forth between Ask Ubuntu and the Killer WiFi module page, and this process resulted in my having to disable Secure Boot and a few other things.

This because the Dell rep who sold me the device assured me I'd be able to just install Ubuntu on this machine and then just run as fast as I could. Yet now I'm stuck with a device that boots in insecure mode, whose GRUB refuses to disappear no matter how much I tweak the timeout settings, and who just doesn't respond well to any UI tweaks I try and add to it ( snappy corners don't work, and playing with another setting overlaid a second menu bar over my dash-to-panel settings so now my desktop is starting to look like the beginnings of a spreadsheet). So... lots of stuff. But I'm enjoying the ride so far, and learning so much. It's actually much better than I expected and overall I love the feel of Ubuntu over Windows.

My question: is there any way I can get access to the same Ubuntu version Dell ships with its American XPSes to put that over whatever I have on mine so I can do a few fresh starts as I continue feeling around this device? Please forgive the ignorance, I just don't understand what else could possibly explain the issues I've been having. At this point I really just want it to work straight out of the gate from here on in.