ADB Clipboard is a small app on your smartphone that allows you to read/write the Android clipboard using ADB.

Features:

Easy to use
Very small app
Does not request any permissions
Python script on your PC to communicate with the app over adb (USB cable or Wifi for rooted devices)
Installation:

There are two parts to install: The app on your test phones and the python script on your development PC. The app you can install from here, the python script can be obtained from the app’s Github repo