I consider SBCs drastically overhyped these days. RaspberryPi was nice enough when it was released a decade ago, but these days you can just get a Beelink or similar miniPC, which is much more capable and often even cheaper. It doesn’t have the GPIO, but even if you need that, you are generally better served with a cheap MCU connected to USB.
I would put it another way; they’re ideal for You Have One Vital Job Only projects; Home Assistant and Pihole are my two specific, but robotics, a router, even a dedicated NAS would be a use case. I could run a lot of things on a mini PC with a hypervisor–soon, I shall start be experimenting with that–but One Vital Job Only projects are ones that do their thing without me ideally ever noticing them other than maintenance, if that makes sense. And even more important, things I should not tinker with because they’re just fine, which is why I ended up building a second, dedicated Media Server/media ripping/encoding/NAS machine; once I did that, I finally had a stable media library I could access for more than a month at a time before I got An Idea That Would Be Fun and Oops Time To Reinstall (seriously; before I built that machine, I had to run my media and plex from a Pi (aka One Vital Job) because if I put it on my main machine, I’d tinker it to death; hence, separate everything. I am basically hiding the cookies from a three year old and I am the three year old).
Tentatively–and this applies to a much smaller population–they’re perfect for deconstructing the Linux kernel and operating systems in general because you get to work at a reduced scale. I have the repository for the Pi kernel in my bookmarks and go to just read through it and get familiar when I have some time or if I remember something I want to look for (my usb wifi dongle testing project was invaluable for how much kernel homework I had to do, it’s hilarious). I know and can write in basic C++, I know how to compile, but I still don’t pretend to understand the kernel; with the Pi’s scale, though, I can grasp it, if that makes sense. I can recognize the structure and begin to get how things fit together. I can even–tentatively–find specific parts, identify drivers, especially when it comes to specific removable hardware where it’s fairly obvious and easy to follow (following actual driver files…that’s in progress). My goal before I die is to be able to read and follow the entire kernel end to end; I think I’m going to need to look into the benefits of reincarnation or cryogenics admittedly, but hope springs eternal.
(BeagleBones–if nothing else–has seriously upped my game on Figure It Out For Yourself. Which yes is a very me-specific use case, requires more homework to get context than literally every class I’m taking combined including TCP/IP class, and I literally don’t have time to do in more than sprints, but did lead to me literally being able to making my first Universal New Install Checklist (covers every Linux operating system I’ve ever used including all my personal configurations and scripts, in order, with all exceptions) and my first foray into creating an auto-install-and-configure script I can run on a new machine. Yes, those Beagles had me doing a clean install that many times. No idea what I’m doing there and I really wish there was a universal template for that.)
Having said that, I haven’t jumped into MiniPC/hypervisor culture so I am up for changing my mind the minute I make the leap. And seriously, this thread has moved it actively up my priority list, which I did not see coming, so thank you for that.