Very interesting project on github..It gives me ideas on how to implement stuff on microcontrollers (Arduino etc.) to control Pianoteq, or have a raspberry button to trigger my preset loading or run the script after starting pianoteq..

For other people I just did the minimum example:
1) Run the local server with

pianoteqPath/PianoteqApp --serve 0.0.0.0:8081

2) from terminal you get the presets with:

curl -X "POST" "http://localhost:8081/jsonrpc" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{
  "jsonrpc": "2.0",
  "method": "getListOfPresets",
  "id": "0",
  "params": []
}'

3) Change the preset to my favourite:

curl -X "POST" "http://localhost:8081/jsonrpc" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{
  "jsonrpc": "2.0",
  "method": "loadPreset",
  "id": "0",
  "params": [
    "HB Steinway D 3 Mics"
  ]
}'

It works fine..

I use Pianoteq in Patchbox OS and i would like to open my favourite preset without display (headless). Pathbox OS can open Pianoteq without any user interaction, but i would like to have my favourite preset open automatically too.

I know Pianoteq standalone opens the most recent preset when opening, but i would like to change presets with a midi message while i am playing, but return to the default when the program starts (it wouldnt be easy to navigate without a screen)

I haven't tried it myself but it looks like you can use midi mapping to change presets: https://forum.modartt.com/viewtopic.php?id=3598

However I do use this little web client to control pianoteq: https://github.com/robert-rc2i/ptq-client-webapp

It works fine after the initial setup of starting pianoteq with "--serve 0.0.0.0:8081" and connecting it via web client.

I know Pianoteq standalone opens the most recent preset when opening, but i would like to change presets with a midi message while i am playing, but return to the default when the program starts (it wouldnt be easy to navigate without a screen)