I've followed a similar progression, and am in the process of adjusting to an XPS 9570 (i7, 4K screen, big battery) running Kubuntu 18.04, from a mid-2012 15" M

I've followed a similar progression, and am in the process of adjusting to an XPS 9570 (i7, 4K screen, big battery) running Kubuntu 18.04, from a mid-2012 15" MacBook Pro. Still on the fence - I really want to like the new machine, but it's not being easy. The only improvements really, are the CPU, the screen, and the weight. I would've gladly paid a couple grand to keep the old machine, with a few MacOS bugs fixed and a more modern CPU. The 4K screen does look pretty, but I still haven't managed to get a workable dual-monitor setup with it alongside a not-4K monitor. I wish there had been an option to buy the not-4K screen, and the bigger CPU and battery, but at least in the NZ Dell store that wasn't available. The touchpad in particular is driving me nuts - the heel of my typing hand will often cause the touchpad to jump the cursor off to the side mid-line. The surprise of seeing some chunk of code disappear has resulted in too much spilled martini. It often mistakenly detects middle-clicks. Apparently, there are two drivers that can work with this touchpad, and the other one has some settings that may help... Lots of crashiness and sleep problems I was having turned out to be the nouveau driver being loaded by a systemd service called "nvidia-fallback" - disabling that helped a lot. A lot of the peripheral experience isn't great coming from Apple-land; in particular the TB16 dock is way overpriced and awkward, especially including the '90s throwback power brick. I'd love to not spend hours getting audio to come out the right port between the computer's headphone jack, the dock's, or the computer's speakers (which, BTW, aren't great).