One apparent option is a namespace package. However, that would require removing __init__.py from the base pymodbus and calling it pymodbus.library or something. Ugh. So I think the least-bad option ...

Thanks for creating and maintaining this package. We are using a ModbusSerialServer with Python 3.11 and pymodbus==3.9.2. One of the connected clients is throwing a stray 0x0 at the end of messages ...