If I follow the instructions in https://developer.atlassian.com/cloud/jira/platform/oauth-2-3lo-apps/#distributing-your-oauth-2-0--3lo--apps , I was able to create a test 3L0 App that works fine.
But the Notice to not instruct customer to create individual 3LO apps, raises a question for me. If i want to create an App that my customers install on their servers (which obviously have differing domains) and that uses 3L0, the Callback Url, will have to differ between customers, but neither in the UI or the documentation have I found anything about setting up multiple Callback Urls.
So how do I set up an 3L0 app that customers with different domains can use ?