Boris:

My wife was/is computer illiterate. She got her Windows 7 laptop
in 2009 at age 67. Uses Firefox to get to Youtube lectures and
has very extensive bookmarks. Doesn't email.

I liked Windows 7. I started using Start8 and Start10 when I
moved to Windows 10. Start10 from Stardock.com is only $5.00 and
makes the operating system feel just like Windows 7. Both
Stardock products make Windows8/10 look/work just like Windows 7
(which you said your kin is familiar with).

Others will tell you there are free add-ons that make newer
Windows behave like Windows 7. (I forget their names.)

Bottom line: If/when it comes to it, there are ways to work
around your kin's trepidation about a new operating system. My
wife's transition from Windows 7 to Start 10 18 months ago was
seamless when we bought her new laptop.

Good luck with the power supply. Hope it fixes your problem.