Here’s the trick:
[some community](/c/some_community@server.tld)
So:
[WowThisLemmyExists](/c/wowthislemmyexists@lemmy.ca)
Gives us this link: WowThisLemmyExists
Which links to that community… but within the instance you’re currently in! So you can actually subscribe to it!
(Many thanks to the Lemmy Project Chat on Matrix!)
Clicking the link crashed my jerboa ☹️
Same here, hopefully that will get fixed soon.