I ran a Dell XPS (not even the Canonical certified version) for a few years at a past job, and everything worked pretty well under Ubuntu. But it's always a matter of which exact hardware combination has mainstream support, and if the version you get doesn't e.g. have a shitty WiFi chip with bad support.

Yes. This is why I rather check Linux support od chips in a machine that I am planning to buy. Not that much work but you will not get unpleasant surprise when Wi-Fi do not work.