Debian
I'm interested in using Debian on my next laptop. The releases are slow, of course, but not much slower than Ubuntu LTS. For a few years now, I've been using Ubuntu LTS, anyway. I've found that many non-LTS releases introduce problems on my machine. Besides, these days, it's not hard to install newer desktop applications using Flatpak and newer CLI programs using… I don't know, Homebrew?
Debian's commitment to free software would have appealed to me more as a younger person, but these days, I want a laptop that just works, and I do see the value of proprietary software. Apple creates great software, for example, and it very often has higher usability and user experience standards than open-source software does. (Liquid Glass is one notable exception over at Apple and Signal, WordPress, and GNOME, among others, are notable exceptions in the open-source community. Also, I really hate the way Apple behaves as a company, but I think that's largely a separate issue.) Thankfully, with Debian, it's easy to work around the free software guardrails and install proprietary software. So easy, in fact, that the FSF faults Debian for it.
What's wrong with Ubuntu LTS? Not much. I like it, and my gripes are pretty minor. Ubuntu does have a habit of force-feeding their users unpopular software that was built in-house, though, like Unity, Snap, and lots of other stuff. I would prefer a pure GNOME experience with Flatpak and Homebrew as alternative package managers. Plus, I think it would be fun to learn Debian. That's the biggest reason I'm interested in switching, honestly.
Maybe some additional thinking will change my mind, but at the moment, I'm interested in giving Debian a shot. I probably don't have enough energy or interest to do it now, though. I'll wait until I buy a new laptop. (I remember installing Arch Linux mid-way through courses at RIT and being unable to use my laptop for one week while I figured out how to properly configure full-disk encryption with LUKS. Yeah, those days are gone.)