ixnay on anything but the vanillaest of the vanillas and that goes triple for bazzite and friends. you don’t want “intriguing” shit left behind to take care of pops, that’s a thing for you to play and experiment with.

your solution is already staring you in the face: the ubuntu you left behind persevered even under those circumstances. either fix it and update it or install a fresh one, with a tweak here and there. and don’t touch nothing else…

Is there something locked down like Bazzite but with long term LTS release cycle?

The only high confidence projects I know of are:

• Bluefin LTS
• Endless OS, also see its documentation

There’s also stuff like HeliumOS, stillOS and probably other images based (in)directly on RHEL Image Mode.

Any atomic distro + flatpak packages.

Debian and install the “unattended-upgrades” package.

You set it up with an email address to complain to when something fucks up and it just works.

E: no matter what you end up going with, some kind of reverse proxy or vpn will be helpful for when you need to remote in and fix something.

If you end up needing Remote Desktop and can do it, stay away from Wayland. The screen sharing situation there is confusing and annoying for seasoned users, let alone in a tech support situation.

What might be a better bet is either a windows (robust screen sharing setup) or mac (simpler interface and reliability) computer. You’re gonna be on the other end of it, so make sure to pick what you know the most deeply when it comes to remote support.

E2: another note in the vein of hated non linux oses: Those might be good because other people in the users life may be familiar with them and it won’t be such a pain when they wanna open a file or something.

Don’t think in terms of easy to use and unbreakable. You won’t get that because something as simple as losing icons on the desktop is the kinda thing that’ll confuse someone that’s bad with computers. Instead, think in terms of what’s going to be easy for you to fix when you inevitably have to play tech support.

Whichever distro you choose, you could set up SSH access for yourself to do things for them (apart from fixing most networking issues if they can’t connect to the internet ofc).

Define what you mean by “locked down”. If you don’t give your user superuser privileges, every distro is locked down because the user can only ever write to their own /home

I’d strongly recommend Mint:

• with Cinnamon DE: very Windows-esque UI
• Ubuntu / Debian-based, i.e. rock-solid, unlikely to break
• 100% automated updates (including automatic removal of old kernels so your /boot won’t get clogged
• Timeshift system snapshots in case something does break. (Note: I’ve only ever used Timeshift to un-fuck systems that I, personally, had fucked with superuser rights and manual meddling.)

elementaryos is great for just this. haven’t used it in a while but i remember it being the most polished user experience on linux.

The distro doesn’t matter, the Desktop Environment does.

If they are used to MacOS and want something simple and “out of the way”, go with Gnome.

If they are used to Windows, go with KDE.

Fedora is probably the most straightforward to install and manage right now. You won’t need to “lock down” anything if you don’t give them sudo credentials.and just a regular user account.

I think more important than which distro to choose is you setting up remote access for yourself. Tailscale and maybe rust desk or something would be a good idea. Or if you want to go further a vpn connection to a KVM device, some of them support being able to wire into the power button so you have full control. I would also have their account info in your password manager. Then you don’t need them to remember anything because you can do it when needed.

FydeOS might be more in line with what you need. Based on ChromeOS, but without the Google account requirements and spyware. I installed this on my dad’s PC along with setting up DNS-based Ad blocking and it’s been rock solid. If he just needs a browser, that’s basically what it is.