User level OH does not have access to the F7 methods.
You may be able to use the new UI item feature, but I’m not sure it quite fits your use case. This has been added very recently so I don’t think it’s even documented yet, but you can see the basic info in the PR here:
This is only works on interfaces where you have configured the UI listening item (as it should be), and it won’t open a photobrowser directly, but you could have it open a widget in a popup that uses the oh-image-card to show you a specific image.