

So I’m a sceptic when it comes to immutable desktops. What you gain in stability you sacrifice in flexibility and control. If you want to use software outside of Flatpak and your distros repos, immutable can be very annoying to work around.
If you want more control and flexibility, a standard install with a Long Term Support distro will be fine. I use OpenSuSE Tumbleweed; I wouldn’t recommend that as it’s a rolling distro but I would recommend OpenSuSE Leap the point release distro. It has good user tools in YaST, it’s secure and it’s reliable, and it has a sensible update schedule. It is also a decent distro for coding. It has multiple versions of Python available which I believe are configured to coexist well, deliberately to make coding and version control easier.
I’d avoid anything directly Ubuntu related due to the reliance on Snap. But Linux Mint is a good variant which has loads of support available online if you want to ease back into Linux. Make no mistake, although it’s user friendly, it’s a full distro and capable of being as powerful as you want.
If you really do want to go down the immutable route, then probably Fedora Silver blue and variants is the way to go at the moment. I second the Kaionite recommendation - KDE is great. It’s well established and popular in the space, so there will more support out there should issues arise (most commonly installing something not in the repos and not on Flatpak). Immutable distros from other big names aren’t really there yet in terms of the user base as far as I’m aware.
Yeah I totally understand that, I’ve played around with immutable distros inside virtual machines and they’re interesting. Also if you like tinkering, Linux is a great OS.
If you do go immutable have a play with KVM - Kernel Virtual Machines - they’re easy to set up and give near native speeds for guest virtual Linux machines (or decent performance for other OS like Windows) It’s a great way to play with Linux inside a sandbox while keeping your host clear; but also a very useful way to run custom software in a flexible Linux guest while on an immutable desktop. E.g. Create a Mint VM to run something that’d be a pain to set up on Silverblue.
Immutable desktop plus KVM guests might be the best of both worlds. Even if you don’t end up on immutable distro, KVM is cool tech that has really advanced in the last few years. It’s better and more powerful than VirtualBox imo, and I use it a lot even on my rolling release distro (I have a VM to run work Microsoft Office, plus a few Linux VMs for a torrent stack and just for tinkering).