Agreed that the best one-stop answer is to tell people to buy their next computer from a Linux specialist (and be able to name 3 of them).

And yes, there's a limit to how easy the DIY solution is going to be. But I think that the bar is now pretty low if we make it as easy as possible. As you suggest, installer software is now pretty much "just hit Enter" until it works. The weak link is now the boot medium. I'm pretty experienced and yet whenever I have installed Ubuntu from Windows I've had to struggle with Powershell (or whatever it's called) and go googling for dd command parameters. The alternative is third-party software, as you say, which has its own security risks and learning curve.

This s a crazy situation. The OS should bundle all software you need to get it running and it should hand-hold the user every step of the way. Big button "Get started", step 1, step 2, step 3, done. It doesn't have to be walls of text full of jargon and useless technical asides (as Debian does it, and even Ubuntu to some extent). And the user doesn't need to understand what exactly is happening, they just need to get up and running. When I was beginning with Linux I had no idea what I was doing but I persisted. So many others are not going to persist in the face of this unnecessary complexity. It really irritates me that FOSS shoots itself in the foot like this.

Rant over. Last time I checked, the specific answer to your question was: Fedora. Big buttons, 1, 2, 3, and the boot-creation binary is right there as part of the process. Probably some further refinements are possible, but Fedora seems not bad.