It's easier to just type/paste in the address of the community on the search page of your instance in the [[email protected]](/c/[email protected])
format.
You can then click the result and just hit subscribe.
Would be nice if Jerboa and the web UI just translated links in that format so that theyd just open from your instance and let you sub instantly.
ATM they just open in the browser and display from the hosting instance, preventing an easy sub.