In practice, what happens in many cases is that you have a separate name for each place. For example, your English passport will say “John” but your Polish one

In practice, what happens in many cases is that you have a separate name for each place. For example, your English passport will say “John” but your Polish one will say “Jan.” The Polish one won’t actually let you have the name “John”, or at least it will be translated by default. So it isn’t always necessary to have a single name that can translate into X languages, but that there is a version of the name in the languages you care about.