As far as I understand, e.g. for iOS you need to fork the app, make your branding modifications and then publish on the app store (need of a developer account, passing through review process etc.).
The desktop clients are perhaps a bit easier in the way that you don’t have the app stores. Perhaps in Europe, with alternative app stores, this might become easier…???
I don’t know if many passed through these steps and documented this publicly.
If it is not just a private project to try out things for the fun of it, it’s perhaps worth figuring out how much the effort is and how much this is in comparison to the enterprise subscription.