Fine points. And I am considering that simplicity might be worth it. Except for:
Another fix might be moving towards software that doesn’t require the capacity to reverse updates frequently.
Totally solid advice, but I love my rolling release distro though. So for the time being I’m willing to accept the associated risk.
I can recommend Debian or Fedora. They are both mature distros that are pretty easy to install and generally work well with minimal fuss and are easy to maintain. I often see Linux Mint recommend, including in this thread. I’ve never used it so I can’t speak to it. But I have every reason to believe it’s a solid choice.
As for transfer process, since you mention using spare disks, NTFS filesystems are supported and you may be able to just copy files off of them. I don’t know if bitlocker is supported.