The current pin from an ESC, all ESC’s, is a voltage equivalent signal from the current shunt resistor and it does NOT go to a serial port it goes to a current input pin which that Flight Controller has.
I think you need to review the available docs for that ESC and the Matek H743-Slim (right on their website, ardupilot mapping) as you are confusing several different things here.
You do now understand there is no telemetry from that ESC so any question about serial ports is meaningless in this context right?
You should:
Flash Bluejay to that ESC
Flash the Bdshot version of firmware to the FC
Connect 7 wires from the ESC to the FC none of which go to a serial port.