Is there something that is good to be a “android” server? I want to sign in to this server for all my chat stuff and use beeper to connect to it. I tried using a tablet but the battery keeps dying.
Cheap, commodity Android box as found on eBay, AliExpress, etc.?
Depends on how real you want your Android to be, but Google Android emulator images and Androidx86 exist. Many of these apps run fine in Waydroid as well. A remote desktop UI on a Linux server/VM may be all you need.
If you have decent soldering skills, there are guides online about how you can replace the battery in devices like these by soldering a resistor and a buck converter to the battery pins so it can run permanently without turning the battery into a lithium bomb. If you set up ADB access you can control the screen remotely using scrcpy, all you'd really need is a cheap second hand phone, 20 bucks worth of parts, and a steady hand.