By installing LineageOS on a galaxy s7 the old phone was turned into a self-hosted Navidrome server, with this approach you can use old smartphones like single board computers. The problem with this could be that depending on the model the battery could overheat if you leave it charging. It would be interesting to have a list of which smartphones are compatible with this approach.
This reminds me of https://slrpnk.net/post/280323, about doing similar things with old Chromebooks. I definitely think there should be a movement toward using random older devices for hobbyist projects. I mean, there’s nothing actually special about the RPi, just that it’s small and enough people use it that they can pre-prepare software for that specific hardware. But it should only be a little more work to make just about any computer do the things that people use the pi for. I think the possibility of a bigger movement is there!
Regarding the battery overheating, correct me if I’m wrong but I thought generally the electronics would keep that from happening. Of course, keeping it always on charge would probably degrade the battery life of the device, but once a phone is on server duty that’s not so much of a concern anyway.
Yes, many smartphones are made so that batteries don’t keep taking in power when they’re charged, but not all of them. I honestly don’t know how to figure out which ones do.