Polarr on Apple platforms uses their Share Extension to bring up a list of applications and services that support photo sharing. When the user selects a sharing service, Polarr provides the image to Apple’s API which takes care of the window switching and data transfer.
Is there a correct and easy way to accomplish a this on Linux in a Snap? I could be wrong, but Gnome online accounts doesn’t seem to be as fully fleshed out as its Apple and Android counterparts. Currently for platforms that don’t have a sharing API, we just use a list of common online services. As a user, I would rather see the apps that I’ve installed and services that I have accounts for.