Does Analog Devices offer a GaN based flyback controller?

No, the existing ADI flyback portfolio does not support GaN FETs. They were developed to drive silicon based FETs.

Can LT8306 have an output of >50V?

Yes, however care should be taken in the design where the set output voltage should reach regulation with in 2.5mSec.

Documents LT8306: FAQ

Tags: LT8306 flyback switching regulators Forward and Isolated Controller