Somehow the EFI partition doesn't mount and it's impossible to troubleshoot via phone, she asked me to put back the old system 😞
I switched my Dad to Linux recently, and set his account up without any superuser access. Updates have to wait until I visit once a week, but it restricts his ability to get himself stuck in any update-related tangles.
Linux has problems, but I'm so glad I don't have to support my Dad on Windows anymore, because that was far less predictable for me. Like the time it decided to upload all his files to onedrive (despite him having no knolwledge of this, or what it was doing or whether he'd consented or not) and made the Internet unusably slow for 8 hours by totally saturating his meagre connection.
He didn't even know about onedrive, just phoned me like "The Internet isn't working, what's wrong?" and of course onedrive is the last thing I'd have suspected for causing that symptom, which made it so annoying to diagnose.
Much nicer now his OS doesn't do sneaky things behind his back, or mine.