There have been efforts, but the ones I’ve seen, have just been attempts to ridiculously overcharge for a custom desktop on Linux.
(Of course, there’s a lot to be said for a basic desktop manager on Linux, certainly a reduced attack window.)
But nowadays, I honestly think that that’s the niche that things like the iPad (and Chromebook) are filling:
Locked down enough that external attacks can’t get footholds, and the user can’t (accidentally) take the engine apart, with a somewhat straightforward UI, that’s also functional enough that the 90-95% of common tasks can be managed.
Is this a good thing? Ask me again later - but it’s a thing nonetheless.
My brother did this for his MIL. He used Ubuntu (Linux), but most importantly, he both talked to her about what she used the computer for and watched her use it when he was visiting.
He made sure all the apps she’d use the most were all one click away, and even pre-bookmarked her favourite radio stations to stream. He also copied over her MP3s and photos. Ubuntu includes default folders called Music and Pictures, so that part was a no-brainer. He put a picture of her flower garden as the desktop wallpaper.
I don’t think she’s ever realised she’s not running a version of Windows, but she loves the setup.
- but it’s a thing nonetheless.