M1 Macs only support two normal displays, and the laptop screen counts as one. The solution Renewed Vision recommends is a Blackmagic playback monitor.

Blackmagic Design UltraStudio Monitor 3G Playback Device with Thunderbolt 3 https://www.amazon.com/dp/B08D6RC8Q5/ref=cm_sw_r_cp_api_i_K09Q3ZR2Q9DBCCJ6CAGY

This will show up as a Propresenter screen after it’s installed but doesn’t act as a regular display.

Ya, we were replacing some 20 year old stuff so I managed to get budget for some more expensive stuff.

You can add one monitor with these, but I have heard mixed reviews. We used them on a PC and had some issues with laggy video. I did read on this subreddit recently that there may be some new drivers available for them.

https://www.amazon.com/Blackmagic-Design-UltraStudio-Monitor-Capture/dp/B08D6RC8Q5/