I agree with a bunch of the comments here but wanted to add that there’s a decades-long legacy of good FOSS/Linux support on Thinkpads. Before any of these companies existed, Linux was running pretty reliably on Thinkpads.

I do like the newer options with these newer manufacturers, but I won’t be getting rid of my Thinkpads any time soon. I’m running a Framework now too.

How does the immutability come into play with Nitrux vs, say NixOS?

I’ve read that systemd-homed can do encrypted home directories but I haven’t tried it, much less on WSL but that may get you to achieve the encrypted home directory at least.

Personally I don’t think I would have a need to encrypt all of WSL, but maybe that also makes sense for your case.

ArchWiki example: https://wiki.archlinux.org/title/Systemd-homed