medialooks Video Transport supports SRT+NDI w/ alpha: Video Transport - NDI Streaming and Video Over IP Software
Video Transport natively supports NDI video with alpha channel transparency data – you can transport both video and graphics (fill & key) in a single stream.
NDI wants key+fill to be in the same stream as BGRA I’d consider CCG to be fully compliant and your issue is with something that’s not compliant with NDI.