Soldato
Well you can use Airplay to Mac, which isn't as good as a native wired connection, but that still allows you to use the mac as screen for another mac.
I don't know if it's me, but I find sustained AirPlay to be laggy, and a little bit unreliable. Wouldn't want to be working off an AirPlay display, but it's an option I suppose if people want it. I just want target display mode 2022.