> It's a good target if you want to provide something very close to a "turn-key appliance" without actually selling your own hardware: You can provide an image that a user writes to a microSD card, plugs in, and it just works.

Better yet - they boot from USB now (and even NVMe if you're using a CM4).

You're missing (IMO) the fun one: PXE. Micro SD cards go bad frequently, and this turns the RPi into a Line Replaceable Unit. Should one ever have coffee spilled on it, a new one is plug and play, with (excluding hardware availability) relatively little downtime.

For many use cases, yeah, PXE is great. Classrooms/labs, digital signage, or anywhere you need distributed I/O, it makes total sense.

The biggest downside is your PXE server going down is going to kill all the Pis, so if you are doing something important you need a highly-available PXE setup. And if you have that, it's probably a better place to host a lot of the services people use Pis for in the first place.

Don't forget http://www.raspberry-asterisk.org/

I've setup a small office with 5 lines + 10 extensions all running on one of those (+ an analog line adapter), and it's been trouble free for the 3-4 year uptime so far.

Oh, definitely a good example, I'm embarrassed I forgot that! I was part of the core FreePBX development team for a few years (before RasPBX was a thing), and eventually moved my home PBX setup to a Pi 1 running RasPBX, which I used for 4+ years.

Sadly, as our usage of the IP phones dwindled (cell phones, texting, and now conference software taking over), my significant other began evicting them from around the house ("too big and ugly"). A couple years ago, my instance was at the point I needed to do some major OS upgrades to it, and considering it was basically my office phone and a cordless left, I ended up retiring the Pi and PBX. Now I just register my last couple phones directly to my VoIP provider.

It looks like a Pi 4 can handle "dozens" of simultaneous channels (though depends on codecs used), and that would be my starting point if I got back into doing PBX work or deploying a system today -- though I'd probably run it from an SSD instead of SD card.

This is a great example of the benefits of the Pi hardware, too: People don't tolerate PBX downtime. With the Pi, it's incredibly cheap to have hardware for a failover server (try pricing that out on a commercial PBX!), and in an emergency you can run out and buy one locally or have it shipped overnight.

OpenElec ceased development around four years ago, you'd be better off with the fork LibreElec which is actively maintained

In my personal niche, there's also http://stratux.me. Commercial competitors are making their own devices that cost hundreds more, but for those willing to put in the few minutes to assemble the RPi and USB dongles into an enclosure, it's very cost-effective.