This. I have been running it the same way for some time now. Even if you change something on one machine and something else on another nextcloud will just happily inform you of the conflict and then you can open both databases and cherry pick. Never had corruption issues.
Vista was truly the greatest Windows I’ve ever used. I had been using 98 and XP when I bought my first Laptop (the first computer that was truly mine that I had bought with my own money) and it was running Vista of course. Being a curious computer user I twiddled with the system a lot and it broke A LOT so I learned fixing (or reinstalling it) eventually I figured out that Windows only lets you get so far in twiddling and customization so I tried out that hacker OS Linux with a dual boot at first and eventually switching completely. Haven’t run Windows as a daily driver since ~2011-12 now working as a Linux Sysadmin. All thanks to that stupid piece of shit Vista :)
For files are in git (using stow to recreate) and my documents folder is syncing to nextcloud (selfhosted) and this also to my laptop. This is of course not a “Backup” per se more a “multiple copies” but it gets the job done and also firs my workflow. To be happy with that I want to set up an offsite backup of data from my server to a NAS in my parents place but right now that’s just a to-do I haven’t put any work in yet ;)
Moved my sister to Ubuntu a while ago aside from the occasional support call everything works quite well.
As for my mom, I sat her down way back and told her she needed to move off of Windows XP (support was running out). I explained to her that she could learn Windows 7 and eventually 10 (8 was already a known dud by then) or she could switch to a “Traditional” desktop paradigm that resembled XP closely where she’d only had to relearn once and then keep running it forever, so I moved her to MATE.
While most issues she had with incompatibilities could be solved (and often remotely by me just via ssh) there was one MFP that just wouldn’t scan properly (I’ve scoured the web for guides and sane drivers etc.) in the end I set up a Dual boot Windows (with a nice "switch to Windows " script right in the pinned apps) just so she could scan from there (scans automatically saved on a NAS share that was also available in Linux so she could use the scanned documents there). These days the MFP died and she got a new one that will actually scan in Linux but I kept the dual boot just in case (though I doubt she ever uses it).