How do I unlock GEO zones with an A3 flight controller?
There is no option to choose A3 on the flysafe map so I don't even know where the restrictions exist: https://www.dji.com/flysafe/geo-map

And if I need to unlock a zone, I can't even find the serial number for the FC in the Assistant.

I do not have Lightbridge as I use a Teradek system. This is a professional heavy-lift system used for on-set filming.

Hello there ianwood. Thank you for reaching out and for these information you have posted. For us to be able to assist you further with regards to this matter. Kindly please send an email to out DJI FlySafe department at flysafe@dji.com for details. Thank you and fly safe always.