What @exi 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.