This is a short but useful snippet of code if you use a Mac to edit your photos that I found on Reddit. This stops Apple Photos from launching when you insert an SD card or any external USB device.

To stop Apple Photos from ever launching again when you connect any device/memory card do the following:
Launch a ‘Terminal’ session
Enter the following line:
defaults -currentHost write com.apple.ImageCapture disableHotPlug -bool YES

There is an option in Photos to stop it loading “for this card” but that doesn’t work if you format the card which is very likely a part of your workflow if you use Lightroom (and it’s more sensible to copy rather than move in case your drive goes belly-up while transferring).