weird, for some reason I wasn't subscribed to this community. Sorry about that! On to your question:
https://lemmy.ca/c/[email protected] will work now, but only because you have to first search for it, either using the url for the instance it's on (https://beehaw.org/c/support) or the following format ([email protected]).
I believe that's just how the federation works on lemmy, if the no one has searched and/or subscribed to the remote community, you will get the 404 error code.
hope that makes sense!
edit: also, when searching for it, give it a good 5-10 seconds for the result to show up. i believe it needs to query the server and takes a bit sometimes.