Hi @Roy-Wood ,
Natively, the RC and PX4IO drivers are looking at UART on J19.
The ESC driver natively looks to J18 (E in the diagram). We've not tried RC on that UART and it's not "easily" configurable through a PX4 param, although I'm pretty sure modifying code could get it going... let me know if you are opening the hood up to the code base and I can point ya towards areas.