I have failed with the limited time available to load 8gb microSD with pyserial to run modbus, modbus_relay, modbus_boards. Modbus & pyserial have to run under (venv) as the install may break some libraries. Despite setting the paths etc I have failed to escape the apt-get/pip, pip3 pipx errors, now other pressing projects can't be ignored. This OS is to run on Pi 3 B, B+ and will be driving chinese RS485 8 way relays. This has to be UK based as I will need the ready imaged SD poated, too large to download. To anyone more practiced this should be a 1hr job - I think !