"For ubitx (V3 or 4) a pair of back to back 1n194/4148 diodes from K3 Pin14 to ground
is the best bet as then its only there for RX and has no impact on TX."
If there is a possibility that these diodes could cause spurs during TX (which I doubt), then it seems the safer approach is to connect the back-to-'back diodes from K1 pin 12 to ground. K1 pin 12 is grounded and isolated from the RX/TX circuitry connected to K1 pin 14 during TX, which guarantees that the diodes can't cause spurs during TX. Placing the the diodes from K1 pin 12 to ground should still provide the same protection for Q90 during receive as connecting them from K1 pin 14 to ground.