By now I've mostly (I think) gotten used to some of Lemmy's quirks, but one caught me a little off guard a moment ago related to the search. Admittedly I was trying to be a little lazy, but I think that's fortuitous as many likely take this approach.
I was trying to search to see if a video was posted here before posting it, as I try to avoid making repeat posts especially in the same community.
So I went to search with the default search settings, copied the video's url into the search and ran it.
Despite the default search type being All, which I think many would expect to include searching by all types (posts/comments/communities/users/url), it seems to exclude url. I found this out as I saw only one comment with the video url and no posts, and so went ahead and posted only to see afterward all the cross-posts to other communities.
In a similar way, searching with the All setting for communities feels clunky, as if one searches by a community name without an exclamation mark, it will only show up as mentioned in comments (if it's been mentioned). There's no sort of fuzzy search to have a direct link to the community display in the results.
These are just a couple stumbling blocks in the default web UI that have been around for awhile, but caught my attention again.
Are you logged in on those instances? Resolving a community name like that requires a network request, if you are not logged in it doesnt work.
Aah, that may explain it! I thought it might be best to check logged out for a better sense of how search worked, so was searching logged out.