Just notice that Rotary Encoder II is still on PR pending status in your list. In the meantime it was released on the Volumio 3 plugin store in stable version 1.0.12
And it moved from User Interface group to System hardware.
Not sure if this thread is still being updated, but I wanted to say that the Onkyo Control plugin has a PR out now.
We need to verify it in order to push it as beta.
We’ll do our best this end of the week…
Thanks to be patient 