I notice that in the link to the RTSP "beta" firmware wyze have removed it completely, so there's no option to use an open protocol any more?

I think the only option for that is flashing custom firmware, which i am not sure can be done on the most recent hardware revisions.

https://github.com/openmiko/openmiko

https://github.com/EliasKotlyar/Xiaomi-Dafang-Hacks