RPi4 not talking to arduino motor driver

[ironman]

... the standalone plugin...

I think we have a terminology issue here - there is no such thing as a standalone plugin, if ever ;-) If you are referring to the pypilot installation from the openplotter (Raspberry→Openplotter→Settings) indeed the openplotter install still reverts pypilot to 0.16. I'll make a mention to this end in the workbook. I have not made a complaint with the openplotter people yet because I cannot ask them to shoot at a moving duck. But 0.16 is a long dead duck.

If you refer to the "(OpenCPN) pypilot plugin" (the little sailboat in opencpn) I assume that you install this plugin from the Plugin Manager in OpenCPN (Options-> Plugins) from the Plugin Catalog: Master. The opencpn plugin manager mentions the plugin version, this should be like 0.30.something

I went into "configuration" and set 127.0.0.1:20220 (same for :10110)and it then shows latency but does not connect to pypilot. 

If you clicked on the sailboat, and then on config, and filled this in the 'host' field, this is incorrect. It should not have a port number, only the host address. And the ports you mention are incorrect anyway - these are for nmea messaging.

Starting pypilot (clicking on sailboat) in openCPN produced the errors shown in the attached files.

You cannot start pypilot by clicking the sailboat. With the pypilot plugin, you can connect to an already running instance of pypilot. I've never seen these messages. They might be due to the incorrect port numbers used.

If I kill running instances of pypilot and run pypilot from cli, is runs okay, the web server runs, connects and I can engage pypilot, all seems good.

Let's take it from here. Can you remove the port number in the host section of plugin configuration, and see if you connect that way?

If running from the cli works, try systemctl start pypilot.

Why does pypilot when running as a service, not talk to the web page?

Running as a service, the socket is either :80 or :8080, but you are already aware. I think you might have run the service from the openplotter tooling after (inadvertently) reverting to 0.16. 

All of this is frustrating, I started from a clean fresh install of raspian buster (could not get new bullseye to work with 7 inch screen dispite suggested dtoverlays), fresh openplotter and fresh pypilot...

That is significant information - you did not use an openplotter image? This is slightly uncharted terrain then. Indeed the versions in the "Requirement already satisfied: " logging of your output is different from mine. However, if it runs ok from the cli, including the web page, you are almost there though. Keep it up!