You don't need LAANC if you're flying inside a building. That's only for flights in the NAS.
For the GEO unlock, you'll just apply like normal, explain where you're flying (inside only), and set the unlock boundaries at the edge of the buildings. Or, you can email
[email protected] and tell them what you're doing. They may be able to help you.
One issue you'll have is if you have issues maintaining GPS inside the building. If you have the unlock on, and you lose GPS, the drone will try and land.