I feel these used/screen-broken phones are an under-used ressource that have usually a much better specs/prize ratio, but are held back by the lack of documentation (and lack of support from distros? Raspberry Pi OS is quite solid).

Has anyone turned one of those into a home-server? If so, which steps have you followed?

I think the problem is more there matter of booting a replacement OS on them, and getting drivers on a supported (read: gets security fixes) kernel.

Personally, my biggest qualm is the spicy pillow syndrome. Spicy pillow means the battery swells up so it is no longer safe to connect to power unattended (to say the least).

I tried using nexus 4, then nexus 5 phone as a ip webcam, always connected to power. Result spicy pillow. Tried using an iPhone 6 as a two step Authenticator so I could see the two step code at a glance from my computer by keeping the screen always on, connected to power. Result: spicy pillow. Tried a ZTE phone as another webcam again, same result.

Ah but wait, the battery in the zte is user removable so can I use this phone which gets USB-C power without a battery? Yes, with an asterisk. I still need to connect the spicy pillow on boot and once booted, it will happily run from the 65W laptop charger with USB-C. Seems like certain things like flash photography will be too much for my charger to handle but for an ordinary IP webcam, it works just fine. It runs android, is several versions out of date, is connected to the Internet, yada yada.

What I personally want when/if this EU directive that requires manufacturers to use user replaceable batteries takes effect is the next step that requires devices to be able to boot and operate (at least actions that are physically/electronically possible) without a battery as long as the device is connected to power. Something like how laptops used to be? They still ran just fine without a battery. The OS and firmware make no assumption that a battery exists to boot. This possibly requires the use of a super capacitor, something like the dash am in my car? I don’t know enough about electronics…

You can reduce this risk with a Magisk module known as the "Advanced Charging Controller."

This tool will allow a limit to be placed on the charging percentage; I have my phone set at 80%, so the battery never spends time at 100% charge which is the most damaging.

https://themagisk.com/advanced-charging-controller-acc/

https://github.com/VR-25/acc