I have two HDMI encoders from https://www.szuray.com/, specifically this model: https://www.amazon.com/gp/product/B07CBMZ24P.

I have been able to get them to work with vMix, though I need to enable a vMix compatibility setting. I also had to configure them to output AAC audio, as that is what vMix supports, rather than G711.

There is one remaining issue, though. If I have vMix inputs configured to stream from these devices, and if for some reason the encoders lose their HDMI signal, then later regain that signal, vMix does not resume the audio. The video resumes fine, but not the audio.

If I right-click on the streaming input in vMix and choose "reset", the audio then resumes.

This problem does not exist when streaming from these encoders to VLC; if the HDMI signal is lost then regained, the audio resumes fine.

FYI, the support contacts at https://www.szuray.com/ have been very responsive and willing to help me diagnose my initial issues. This problem appears to be with vMix, however.