Unfortunately you chose the wrong distro for your friend - Linux Mint isn’t good for gaming - it uses an outdated kernel/drivers/other packages, which means you’ll be missing out on all the performance improvements (and fixes) found in more up-to-date distros. Gaming on Linux is a very fast moving target, the landscape is changing at a rapid pace thanks to the development efforts of Valve and the community. So for gaming, you’d generally want to be on the latest kernel+mesa+wine stack.

Also, as you’ve experienced, on Mint you’d have to manually install things like Waydroid and other gaming software, which can be a PITA for newbies.

So instead, I’d highly recommend a gaming-oriented distro such as Nobara or Bazzite. Personally, I’m a big fan of Bazzite - it has everything you’d need for gaming out-of-the-box, and you can even get a console/Steam Deck-like experience, if you install the -deck variant. Also, because it’s an immutable distro with atomic updates, it has a very low chance of breaking, and in the rare ocassion that an update has some issues - you can just select the previous image from the boot menu. So this would be pretty ideal for someone who’s new to Linux, likes to game, and just wants stuff to work.

In saying that, getting games to run in Linux can be tricky sometimes, depending on the game. The general rule of thumb is: try running the game using Proton-GE, and if that fails, check Proton DB for any fixes/tweaks needed for that game - with this, you would never again have to spend hours on troubleshooting, unless you’re playing some niche game that no one has tested before.

First of all you should have asked what he wanted to do with the laptop, the moment he replied playing games that are not on Steam you should have let him use Windows. Secondly, a laptop with 256GB of disk is likely going to have very low amounts of RAM and an onboard GPU, performance is going to be shit on Windows as well, you should have let him use that before, I think it’s highly likely that Windows itself would run like shit on it, so after a year or two putting Linux on that laptop would have blown his socks off. But the problem is that he didn’t get to experience any of that before you touched the computer, now he will claim it’s your fault that games don’t run or Windows is slow. I’ve been there, a friend had issues with the laptop, I said I didn’t understand Windows and would only help if I could put Linux, at first everything worked great, but then the friend needed special software that wasn’t available so I had to reinstall Windows for them (and btw, you OBVIOUSLY should reinstall Windows for your friend), and then everything on that laptop was my fault, even the problems the person was having before were somewhat my fault because I had put Linux there.