Fedora is probably the most mature immutable desktop distro right now, both Silverblue (Gnome) and Kinoite (KDE). I use Kinoite on my Thinkpad x270 and it's been perfect so far.
Ubuntu will release its own version, Ubuntu Core Desktop, “soon” (got delayed earlier this year)
Another interesting one is Bazzite. Inspired by the Steam Deck OS but runs on Fedora (instead of the Steam Deck's Arch) with all the possible Nvidia, AMD, and other gaming enhancements enabled https://github.com/ublue-os/bazzite/
Basically, most of the system is read-only and updates/rollbacks are atomic.
This approach means classical distributions can enjoy some of the advantages of NixOS.
Presumably this means that the operating system is effectively read only.
This is good for applications where you want things to be very stable.
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.