I’ve no real streaming experience, but have a look at Video Stream from OBS Studio. OBS can use hardware acceleration if available, although I’m not sure if you can use it to stream for displays at onces. Results might still vary as packet loss using multicast/rtp/udp transport instantly corrupts the output on the receiver.
I’m curious what kind of use case you’re trying to solve. It sounds easier getting a video card with for output and wiring up the HDMI cables directly to the screens.