Some of the rack mount ATEMs with SDI inputs support not just Program out but preview channel out via a code patching of an Aux Out,(I've never done this myself but am told it's possible). How about the ATEM mini Extreme? Tech Spec (
https://www.blackmagicdesign.com/products/atemmini/techspecs/W-APS-17) says two outputs (well two HDMI are shown in illustration, specs say 4 outputs and 2 Aux outputs but only appears to be two video outs and the rest are audio, ethernet and USB-C).
So if not current Preview channel out, what is the second output?
Is there a way to stream to another device the recording outputs of any of the HDMI inputs in the Mini Extreme ISO? The ISO variant is designed for additional recording of all 8 channels plus program out (how it does that over USB-C I'm not sure, heavy compression and lots of GPU processing power I guess).