Linux

I currently have an older relative using Debian/KDE with unattended-updates and few issues over the past year. Laptop was previously Windows 10, has had replacement battery and HDD->SSD swap, wouldn't be supported by Windows 11, but is totally capable of running most modern apps.

Browsers can just be flatpak/snap/ppa and auto-update whenever, as Debian’s packaged (ESR) versions might get a bit dated.

From my own experiences with Ubuntu variants, I've always had some kind of issue when doing a release update, so I've personally stopped using it, but maybe thats just me.

Only significant issues I've encountered are with some flatpaks needing permission tweaks to (re-)enable printing, webcam, or filesystem access, and potentially over-doing the ad-block extensions/settings leading some sites to break - its worth setting up multiple browsers to pre-empt and work around those problems.

For remote access, it's not a problem in my case, but you could potentially just setup a VPN with something like tailscale and just ssh over that. Once connected, I'd explore systems like VNC or KDE's built-in remote access system. In the short/medium term, it would be easier to stick with X11 for that, but at some point, Wayland and those supporting tools are going to reach parity and distributions/desktop environments will drop X11 entirely - best to future-proof as much as you can.

For regular maintenance, it's worth checking-in regularly to make sure the system and user is happy, and maybe setting a cron-job for house-keeping tasks (removing old kernel files and temp files, checking disk-usage/health), and having that notify you. But that probably depends how physically hands-on you'll be.