There is a person who has turned an obsolete calculator into a Bluetooth wireless keyboard. A user who lost use of an HP48 calculator found a different recycling method.
By adding a wireless Bluetooth connection (Adafruit Feather nRF52 Bluefruit), the inside of the wire is tangled, but the function has been changed so that you can use the smartphone app by connecting wirelessly.
I used the open-source calculator emulator (Sébastien Carlier Emu480), and I programmed each button in the software to react when the keyboard was pressed. Details can be found here.