What @exi@feddit.de said. Switching .deb based distros is little more than changing sources, maybe some pinning, doing an upgrade, and optionally a cleanup pass to remove any stranglers.
My main Linux box is a Debian-Ubuntu-Debian upgrade, that hasn’t seen a proper reinstall for like 15 years (switched all the hardware several times, still no clean reinstall).
Switching between non-deb distros is also possible, with a chroot. Like, Gentoo to Fedora. As long as the kernel is compatible with the glibc, it’s basically like running containers, just on slightly hard mode.
I know what I said. Linux upholds the “don’t break userspace” contract pretty well: most kernels, particularly those from generalistic distros built with modules, are compatible with whatever userspace binaries you throw at them. Major version changes in glibc (or equivalent) is where incompatibilities start, but those happen quite rarely, and you can often still force multiple glibc versions to run side by side.