I haven't really given Standard Ubuntu a chance yet, because I don't like the direction they're going in recent years (different topic). But will definitely consider it, if my issues persist.
My XPS is a work laptop and I haven't used Windows for work in over a decade or so, which makes switching a potentially bigger undertaking ... which I might avoid, if possible.
Thanks for the cable length tip! Hadn't considered this and am using a 1,20m+ cable -- will definitely try a shorter one.
My understanding is that Mint is heavily based upon Ubuntu and assumed there might be none such differences. Thanks for the suggestion -- I will definitely investigate in that direction.
I am regularly checking for updates using fwupdmgr. Did a few updates and things improved a bit. Did not try and firmware-update the display yet ... because I didn't know that was a thing. Thanks for the hint, will check that.
EDIT: I'll also check for a Windows tool, to see if it offers more updates.
I am happy for you, having a positive experience -- and partly because of that, slightly optimistic that Dell might improve my and my peers' situation.
And of course you are right: A single anecdote is just that, but a few more may paint a rather well-rounded picture.
I made an account just to share _my_ experiences with a Dell XPS 9300, Dell WD19TB and one Dell U2719x Display, running the latest Linux Mint, in Cinnamon flavor. There's a reason, I'm spelling out Dell so many times here, because my expectations were that such an all-company-x setup would work out of the box with the least amount of problems. Sadly it did not. Currently the setup is workable, but what I've experienced in the half year I'm running it was nightmarish. The thing wouldn't power up, screen would black out and not come on again during meetings, display must stay on all the time (no power safe), sleep is impossible because the system won't come up again or go to sleep again after a few seconds of waking it up. Web research has lead me to believe, that I'm not the exception, but rather the rule and there might be a reason Dell is still sending out firmware updates for the XPS and the dock (which in general is greatly appreciated). I have to add, the Laptop sits closed in a stand behind the screen, which might contribute to my problems, but I just couldn't let this 100% recommendation stand here without an opposite experience ... I hope this it's working out better for everyone else, but this is my "story". Dell support is no great help either and a time investment I am not happy to make anymore after several tries.
Thanks for the cable length tip! Hadn't considered this and am using a 1,20m+ cable -- will definitely try a shorter one.