You need to attach the Lemonrx to the DSM port, 3.3v, GND, RX3 on the front edge of the fc.
Once you’ve done that connect to Betaflight and flash SPRacing F3 EVO firmware, I’d go with 3.1.6 as it works reliably.
Then connect to betaflight and set uart3 as serial port, save then select serial rx provider and choose spektrum 2048 for dsmx, save.
Go into cli and type “set spektrum_sat_bind = 9” enter, save, enter.
Unplug the fc and when you plug in again the rx should be in bind mode, flashing led. Bind with tx then power cycle the fc and check it’s bound.
If at any stage it doesn’t go as hoped, we can get it sorted.