Trigger a Flow on Specific Domains
There are two ways that allow you to trigger a Flow on a certain domain.
First, from the "Trigger on domain" option in the targeting criteria.
Using this option, you can simply select all the domains you'd like to trigger the flow on as shown below.
The other way is to create and target a user segment that has the "hostname" attribute set to the domain you'd like to trigger the Flow on as shown below.