As far as I can find, it depens on the type of license Per App Plans or Per User Plans:
"Power Apps Per App Plans are scoped to apps in a specific environment, so they cannot be recognized across tenants. Power Apps included with Office and Power Apps Per User Plans are not bound to a specific environment so they are recognized across tenants in guest scenarios."
First of all thanks for the replay, but in this case both tenant users have the same license but still the environment wasn't listed in the guest tenant and the only thing I can see an App that I shared from the other tenant and its a Microsoft stock one.
We can only access that app through the invitation URL and other than I cant see that from anywhere in the app tab.