This has been my experience as well.

So, background: I've maintained computers for various people close to me for maybe 6-7 years or so. A couple computers for my mom (laptop and desktop, with both replaced once or twice), two laptops for some younger cousins going through middle/highschool, a desktop for an aunt, and 2 of my girlfriend's laptops over the same period.

At first, I was very pessimistic about how well it would turn out. For my cousins, the thing that drove me to it was observing how overrun their computers were with viruses, adware, and spyware from all the .exe files they randomly downloaded which claimed to be games, to the point where their computers were more or less unusable (their fans would be blowing full speed and the whole thing overheating from the moment they started, it was kind of surreal). My mom had similar issues, though not quite as bad, mostly from email stuff. Over time, I grew a bit more confident in being able to manage this sort of thing, and now it's my default for this sort of situation.

So, some of the benefits I've noticed:

1. It's a lot easier to dictate terminal commands over the phone or through email than to walk someone through gui operations. If the person struggles enough with computer stuff that they can't even manage with the help of 'user friendly' interfaces, optimizing for the ease with which you can trouble-shoot and fix things over the phone is a lot more practical than chasing after the lost cause of finding a friendly enough interface for them to manage on their own. You can write an important terminal command on a post-it-note next to their compute. You can attach a shell script to an email. Or, with a little bit of setup, you can just ssh into their machine remotely whenever they're having troubles to fix it from the comfort of your own home.

2. It's very easy to set up a minimal, XP-ish interface where all of their needed programs are just right there in the start menu, and such that it's very hard for them to mess up their system such that that base level of functionality is impared.

3. Runs well on fairly limited hardware.

Some general advice if you're considering doing the same:

1. Keep a text-file with all the stuff you installed/changed on the persons computer so you can reproduce it easily in the future.

2. This is more general advice, but have separate / and /home partitions, so you don't need to move their data back and forth if something happens to the OS.

3. Look up issues with their machine and linux ahead of time before trying. It's not always a simple "you can't", sometimes you'll find out there's some firmware you need to install for their wifi to work properly etc.

4. Figure out how much autonomy they should have over their machine. If you're sort of hoping for them to be able to choose and download software on their own, and be able to try to figure out menus to configure stuff, Ubuntu or Linux Mint might be a good choice. Otherwise, surprisingly, Debian might actually be easier for both of you. I've generally found Debian stable just has fewer surprises once it's set up, and you can for the most part just ignore it for years in a way that always seems to go badly when I try it with Ubuntu or Mint, thus lowering the burden on you in maintaining it quite a bit (versus figuring out wtf happened with some random Ubuntu update, or troubleshoot for the umpteenth time how Mint screwed up apt). Decide whether they should actually have sudo privileges or not.

5. Only do it if you're prepared to be their first contact when something happens, and conversely, make absolutely sure they know to contact you first whenever there's a problem. There's nothing more frustrating than a neighbor who thinks they're tech-savy poking in, only to 'fix' things by reinstalling windows, or convincing them they must have a 'virus' because they don't understand what they're looking at.

6. MAKE SURE THE DEFAULT SAVE FORMAT FOR LIBREOFFICE IS doc NOT odf!

7. It'll feel kind of icky, but make sure you have their root password written down on a piece of paper somewhere safe. They will never remember it, and if you give them a piece of paper with it on it and tell them "absolutely do not lose this", they will lose it. Also, more general, but pwqgen is a pretty great program for generating random passwords that are fairly easy to remember.

8. Configure it to work with any home printers they need, and just set their expectations that they will not be able to figure out how to make other people's printers work with their computer. Configuring printers is a discount hell run by a counterfeit Satan.

9. Make sure they have adblock on their browser.