Disable SIP with third-party GPU
You should be able to use the keyboard in order to boot into recovery mode and execute the command while "blind". Do the following:


Boot your Mac while holding down the ⌘+R keys.
Wait 3-5 minutes for your computer to boot up. It will likely boot more quickly than this, but better to be safe.
Press the following sequence of keys:


fn+ctrl+f2 (leave out fn if it's not on your keyboard)
→ x4 (press the right arrow key four times)
↓ x4 (press the down arrow key four times)
enter

Wait around ten seconds to give the terminal time to open. Then, type csrutil disable and press ENTER.
Wait another ten seconds, then type reboot and press ENTER again. Once your computer boots back up, SIP should be disabled.


This was tested on a 2015 Macbook Air running macOS 10.14.1.