Ubuntu has unfortunately become the Windows of the Linux world - and I don't mean that in a good way.
Unless you want to be the perpetual IT support for your parents, I would recommend getting a user-friendly immutable/atomic distro, like Aurora[1]. Aurora uses KDE, which most Windows users would find familiar. It is immutable, which makes it very hard to break, and it uses atomic updates (basically updates either apply or don't: there's no partial state which can break the system). And in the rare event that something does break, you can boot directly to the previous version right from the boot menu, no need to run any manual rollback commands. My 70yr old mother also uses Aurora and has zero issues.
In my experience, if you aren't dealing with power users, normal people won't be able to break their Linux install. The standard permissions model stops them from doing anything stupid, and they don't know enough to be dangerous.
Thing is, regular Linux distros are most prone to breakage when it comes to updates - especially Ubuntu and Ubuntu-based distros[1]. My elderly mum is non-technical and has been a Linux user for the past decade, and she had Xubuntu, Mint and Zorin - all of which ran fine until update broke it (and this is just a bog standard DELL Optiplex desktop with an Intel iGPU). So I switched her to Aurora a couple of years ago and it's been rock solid.
This is why I recommend immutable/atomic distros for newbies, especially if the person installing it doesn't want to be a 24x7 tech support for that user.
I would be very surprised if Debian stable ever broke anything. I am on Debian testing and none of the "standard software" - browser, office suite, image editing, zoom - has broken in many years.
Sure, if you stick to stock Debian repositories you should be fine. However this guarantee is gone if you're using proprietary kernel modules, like say nVidia drivers - which is not an uncommon scenario.
Also, the /usr merge thing has caused some issues for users, requiring manual intervention[1]. Not a big deal for techy users familiar with the terminal, but this isn't something end users might want to deal with.
Image based immutable distros don't have issues like this.
I switched from Arch to Ubuntu a while ago (switching from desktop to laptop, thought the batteries-included experience would be easier). I had, I want to say, a decade old (maybe more like 7 years) Arch install… never experienced a computer thing more annoying than updating Ubuntu.
Would highly recommend Mint. Very stable, sensible defaults. Updates never broke anything in the past several years I have been using it on desktop and laptop. Just install the latest LTS version, turn on automatic updates and forget about it.
Canonical keeps packaging things like Firefox as Snaps and that leads to weird issues sometimes. If it were up to me, I'd avoid anything using Snap because of the potential for headaches.
I wouldn't rule out a distro like Rocky Linux or AlmaLinux (or anything else based on RHEL) with Gnome or KDE installed. They will receive 10 years of kernel and OS security updates, and you can either use Firefox from their repos or use something like Flatpak or Snap to get newer software packages if necessary.
20 years ago Ubuntu was the go-to for baby's first Linux. Is that still the case?