Unfortunately the way Discourse uses hashtags is currently incompatible with the broader use of hashtags in social media… so this seems difficult.
For example #plugin converts to Plugin, #activitypub gets converted to activitypub… these are internal forum references and the context they are used in is different.
I might write something like this in a post for example,
Keep an eye on Announcements for new features!
which wouldn’t make sense off-site when federated as #announcements