The idea was to have the required infrastructure to continue working with whatever I had at reach.

I had an 8-year-old iPhone 6 (last one with a 3.5mm audio jack), on which I had replaced the battery and therefore would last quite a bit. However, the OS was limited to iOS 12, which would prevent many modern applications, requiring higher iOS versions, from working.

The phone had its mute button stuck on mute, cracks in the screen from many falls (however none prevented viewing the screen), the side-power-button was failing and the volume buttons were getting stuck because of the many falls resulting in chassis dents... I really liked this phone because of its tenacity and robustness despite my handling of it. Say what you want about Apple, their products are built to last.

I also had a Keychron K3 Bluetooth keyboard I used daily, which fitted the BOM and project aesthetic quite well. This particular keyboard had a Bluetooth device quick-switch feature, making it simple to work using multiple smartphones/tablets.

Connecting the Bluetooth keyboard to the iPhone was straight forward and allowed to input text via the keyboard.