There are browser extensions that make sure any link opens in the user home instance. And I think there were recent improvements recently to improve the UX in those cases.

There's always the true known universal way which is get the url and past it in the search box of the home instance. If installing a browser extension is too much for most users.

It's obvious we are not at peak perfect UX, and work needs to be done and will be done eventually, but it's not having to learn 2 or 3 new things that should be seen as a blocker to using it. Facebook and twitter were very intuitive at some point when nobody knew how things worked. It's all about learning how to work with it.