The best way is going to constantly remind people that there's alternative ways to see the same content.
Because most people are used to centralization and never ask themselves if there's different ways to access the same content.
Even on Reddit, where third-party apps were wildly popular, most users were still shocked third-party apps were a thing, and many didn't understand why someone would even want that.
It's not gonna work unless there's prominent users with loads of followers around to remind people it works more like email addresses than plain Threads handles.