TLDR: Is it normal to distro hop after being using a distro perfectly for so long?

I have used the same distribution (Debian) for over 20 years when I decided to change distributions and switch to NixOS. Debian was - and still is - a very fine distribution. I just needed something radically different.

So, to answer your question: yes, it is perfectly normal. Two years isn’t even long.

If they have no desire to maintain/sysadmin their own linux systems, then the best distro to recommend is whatever you can help them with, and possibly even maintain for them.

Case in point, my Wife is a very happy NixOS user, despite knowing absolutely nothing about Linux. Yet, she’s on a distribution that’s as far from being newbie friendly as a distro can possibly be. She’s still happy with it, because I set it up for her, and I maintain it for her, she never has to install, upgrade or configure anything, ever.

I’d say “under no circumstances”. When building for production, you want to build on a stable foundation. LFS isn’t that, it’s an educational tool. It does not result in a maintainable, robust system. It requires tremendous amounts of work to keep it secure and updated: there’s no package manager, no repository you can pull from, no nothing. You have to build an entire distribution on your own. Outside of educational purposes, I’m having trouble to imagine any situation where that might be a good idea.

No, not even embedded. There were always distros targetting embedded systems, LFS was never a good choice there either. It was much more straightforward to strip down - say - Debian for a limited device, than to build something from scratch for it. (I spent a few years building and operating embedded Linux systems at the early 2000s, we built it on a stripped down Debian.)

My Emacs needed a bootloader.

I have Emacs, and I have my NixOS configuration. That’s all the GUI system configuration I need.

I’m one of those crazy people with / and /home on tmpfs. Setting that up is very easy with Impermanence, but it does require some care and self control. That is precisely the reason I set it up: I have no self control, and need the OS to force my hand. Without impermanence, my root and home fills up with garbage fast. I tend to try and play with a lotof things, and I abandon most of them. With Impermanence, I don’t need to clean up after myself: I delete the git checkout, and all state, cache and whatnit the software littered around my system will be gone on reboot.

In short, Impermanence makes my system have that freshly installed, clean and snappy feeling.

The whole thing sounds scarier and more complicated than it really is.