Out of curiosity what did you install ? And what did you install it on ?

I changed my grandad onto GNU after I've distrohopped a few times on my system just so I knew how to do a system install (which is a skill in of itself no matter what OS you are installing)

All the major technical issues for install like getting to boot, display driver issues, etc are solved. Even Nvidia is reccomending people use their open source kernel modules (nvidia-open)

That was likely some kind of kdump error, interested to know what distro you used, I often advise people to use a stable but stale distro like a Debian based distro: Mint or Ubuntu is ideal for stability and ease of install.

I setup my grandad on Mint 2 years ago,was fine but decided to hop to Archlinux KDE Plasma as needed some newer stuff(if you enable the incremental backups its not hard to switch if you think a different one is a better fit), even though Archlinux has a reputation for less stability it's been pretty good the last year, avoided AUR *mostly for stability, pamac for GUI updater.

Most of what he needs is in the browser and printing. (Printer issues are OS agnostic nowadays as modern printers seem to be very anti-consumer and they mostly use software to make their money, I.E DRM on ink cartridges)

Only issues my grandad had are printer or website related.

(Detail: used the CLI installer)

(DISCLAIMER: I am a qualified computing professional who have used GNU/Linux as daily driver since 2016, for newcomers a Debian based distro would be more the route I would).

Sounds like a hardware issue, so ...