Tried this with my mother. I had to rebuild the machine with Windows 11 LTSC afterwards. Which she hates but less than Linux which was totally unusable for her.
YMMV but this isn't a real option for a lot of people.
My 87 years-old dad has no idea what OS he runs and migrating a laptop to KDE gave him a stable system with none of the confusing commercial offers, uncontrolled upgrades and forced account creations.
I've been pondering switching to Linux for my mother in-law that has a pretty limited use of her computer (online groceries, emails mostly) and their page is pretty unconvincing in that case. I mean yeah OK, you guys have extensive customization, virtual desktops and all the bells and whistles that appeal to power users, but is it easy to put it in the hands of someone else without having to do customer support all year long?
No - support was the problem. I was spending an hour a night helping her through things. It's not just "stupid users can work it out" situation. It's like moving to another country. And there isn't a lot of information out there to solve a lot of problems. And it's even worse trying to do phone support with someone who doesn't understand what they are looking at because it has all changed.
One cost me a 100 mile round trip to turn airplane mode off after I assume she'd accidentally whacked the mouse wheel button on the icon instead of the browser which for some completely unknown reason does that?!?!?!?! I'm not sure that was even what she did but I spent ages trying to work out how she could have even done that in the first place.
Try again with Ubuntu’s Gnome if you’ll have an opportunity. The “problem” with KDE is that it tries to look like and behave similar to Windows, but it’s not, so older people that remembered how to deal with one UI are confused when what looks similar in reality behaves differently. And it results in frustration.
Gnome, on the other hand, provides a totally different UI, so user immediately identifies that it is different and needs to be learned a bit. But thanks to Gnome being pretty coherent and simple in how UI works, it usually takes very little time to learn and then they just keep using it. I experimented with my parents, father is 70, mother 65, and they both earned default Ubuntu very quickly and don’t have any issues using it, unlike win10+, which constantly raised questions and frustrations that something changed (MS likes to bring idiotic widgets to panels and menus after updates no matter that nobody asked for them).