It's not fast today, but it's possible and portable.
The situation I imagine for this is that a big solar flare comes and takes down the internet for the foreseeable future. There's all kinds of things that are going to stop working because they want to phone home, but cant. Many of them will just be trash at that point, but some can be hacked to respect some other server on the local LAN--that server might be a repurposed phone.
These might be important things. Farm equipment, thermostats, vehicles... The more control we can have over hardware that'll be easy to find, the better.
with smartphones you have, i can't even ballpark a number... half chips are SoC in disguise which hardware changes every week then on top of that there's a custom firmware backed for each customer. multiply that for each little piece of the device.
there's a reason Android alternatives are stuck on last released kernel version: they just copy paste the binary drivers
thing is, smartphones are the most popular sbc on the planet
I've used Termux to run utilities like ffmpeg and imagemagick on the go. I think one of the limitations for graphical usage might be the limited memory space that it's sharing with Android. It's intriguing that this usbredirect setup allows swap space allocation without root.
That's wonderful, and a hundredth of native speed if you are lucky.
The example boot log says 2000 BogoMips, so about a fiftieth of the cpu speed of a contemporary entry level laptop, to a very rough approximation.
Also, no hardware graphics acceleration.
There are some possible uses I suppose. Including the charger and a 3.5" USB hdd I guess it could burn 20 watts to download or upload some torrents, run a IRC client, run a local dev web-server or whatever.
If you have a smartphone and don't have a raspberry pi or other SBC and have some use for an under powered Linux box then have fun.