In general, it is advised not to connect any of these pins to GND. They would be better left floating (maybe with some extra PCB traces laid out so you can probe them easily if troubleshooting is needed);
1 GPI
2 LMN1
3 IN1+
4 IN1-
11 ERRB
12 LOCK
28 LFLTB
For IN+/IN- it is better to connect via a coupling capacitor and 50 ohm to GND.
For LMN_ ideally, you could put the full line fault circuit (45k, 5k, 50k) entirely next to the pin. Otherwise simply leave it open. If you MUST ground the pin, please use a 50k to GND instead.
For LFLT, ERRB, LOCK, you should use a pullup to IOVDD instead. If you MUST use GND (which I am advising against), use a resistor in between so you desolder it and use it for debugging purposes.
For GPI, you should use a resistor to GND.