This is a walksnail Avatar V2 Antenna mount for iFlight Titan XL5 frame.
The original model seem to have an error, the mounting holes are too close to each other, it should be ~25mm.
This was fixed here, by scaling up the original model by 15% and shrinking both the mounting and antenna holes to the correct size. Fusion360 design attached, but it's just an import of the original model and some cylinder.
The author remixed this model.