Its not just a fedia or mbin issue.
Experienced the same on lemmy a few times already. Depending on the size of the instance and the followed communities on there it can be difficult to find communities and people here as well. I just had that a few days ago where I searched for a specific post I knew existed, and I tried to find it couple of times, experimenting around. Once I copied the url I was able to follow, but I still couldn't see the comments, as this maybe needs a bit of time. It's all a huge mess, which can be frustrating.
Maybe it's better trying be patient and to find ways to work around it. I sometimes check out other instances, e.g. fedia.io and just explore from there as I'm curious to see what's new. Way easier to just do this in the browser. Issues with clients sound familiar as well.
Magazines should be able to follow hashtags at least, as far as I know.