Minimum flight controller handshake and FPV

Hi all,

What’s the minimum requirement of setup for the FPV viewing and for Solex to be paired w/ the air unit?

I am trying to access which of the Mavlink commands is need for the air unit to report it is connected to the controller. Is this just heartbeat or are they looking for multiple of the common Mavlink commands? We’re setting up a custom flight controller BBBlue ROS image w/ MAVROS and trying to integrate it with the controller.

What video format does the Herelink support? Does the uHDMI require a go-pro input, or is it okay with PAL/NTSC? Does the flight controller have to specify that an FPV system is attached?