Indoor use is not supported (at time of writing).
The SDK requires that connected vehicles have a position estimate. Currently, this means that GPS is required. In the future we also expect PX4 to support local positioning methods (optical flow or visual-inertial odometry), at which point indoor use will also become possible.
I’m not sure about MAVSDK specifically, but PX4 certainly supports flying (in position mode) with a so-called local position estimate (based on for instance optical flow or visual odometry, as opposed to GPS). The EKF in PX4 has flags to indicate whether the local and/or global position estimates are valid.
I know that. I’m already flying indoors. My question whether I can use the MAVSDK to program the drone.