Is there a way to host two gateways on the same PC?
Only via virtualisation/docker
Yes, there are a variety of ways. The two main things that will conflict are the ports used, and the service name (on Windows). You can rename the Ignition service to something else in the installer, and remap all the ports, but it’s a bit tedious/error prone. A potentially simpler option for development purposes is to use Docker containers; you can easily stand up 1, 2, 10 Ignition containers provided you have sufficient system resources.
I would highly recommend against ever running two Ignition gateways for production on the same system, though VMs are fine, managed correctly.