Will you be recommending Linux instead? Or Win 11, with ads galore? My question is only half joking, I‘m not aware of a good low maintenance alternative.
I installed XFCE desktop on Manjaro (I believe) on my grandma's computer that I bought second-hand a couple years ago for about $60 (i5 6th gen, 8 GB RAM, 120 GB SSD). There have been zero issues. Windows was a nightmare because it was constantly breaking or needing an update and Macs would be wasted money in this case. The usage is pretty light: downloading and sharing photos from a camera, YouTube, email, news, some light spreadsheet accounting, and that's about it. Neither of my grandparents are tech-savvy (my grandpa still uses a feature) and yet they both learned all, that they need, in the afternoon I installed the computer. Zero regrets going for XFCE (or anything that can be stripped down just to the features they need) and buying a cheap computer. Going Windows → Manjaro/XFCE reduced tech support calls to me from 1–2× a month to once per year.
Similar experience for me with my mom. I set her up with a desktop machine running Pop_OS! with automatic updates. I did some minor hackery to get Windows' FreeCell working on it because she cares a lot about that.
I installed tailscale for remote support, but haven't had cause to use it.
In general it's working fantastically.
The only issue is that the USB WiFi adapter drops out rather frequently. So my one hardware concession will be to replace it with one known to be more reliable under Linux. [0]
[0] I know sometimes this can be fixed by choosing a more appropriate driver and/or Bluetooth device settings, but it's not something on which I want to spend a lot of time or headspace.
When XP finally got killed, I set my dad up on Ubuntu LTS with MATE and he ran that way for many years with no issues. Occasionally hardware would fail (like the soundcard) which I would replace with a USB option. All in all though it was great for him. A couple years ago Ubuntu started demanding a "Pro" account/license (which shouldn't have been needed, it was the most recent LTS at the time) and making updates a pain for him, so I switched him to Gnome on Fedora (same setup I use) and it took a few minutes of orientation, but now he absolutely loves it. Absolutely I would recommend Linux instead.
My Gentoo GNU/Linux system is lower maintenance than this. If I don't want an app to launch I simply remove it and it's gone forever. It's a super-basic system that only does what I want and is therefore really easy to maintain.
