Update - At least with a GV-EBD8711 8 Mpix eyeball camera with v1.06 firmware, you can set the main stream to H.264 and HD and use whatever authentication you want. Downside is you lose all the resolution you paid for and can’t get it back on another substream for your NVR.
I’m 99% sure the problem is with Geovision Firmware in that it always returns the main stream video regardless of substream path given.
To get around this: You can use a sub stream set H.264 and HD resolution. H.264 (vs H.265) is required by Alexa and HD is the max resolution since Alexa isn’t able to downscale video.
You must turn off RTSP authentication, and use the RTSP path: rtsp://aaa.bbb.ccc.ddd:554/media/video#/video
Where video# is either video1 or video2 and correlates to the substream you want–video0 is the main stream
Downside – your camera will be open and without a password to view and hear audio via RTSP to anyone that can connect directly to your camera network. You also might not get audio since RTSP DESCRIBE handshake isn’t really occurring and instead going directly to the media source.