Jerboa

As a workaround, if you login with your account on the web site you could subscribe to your desired communities and then they'll show up in jerboa.

To view a community on another server from your server, in the search box put "!community@otherserver.com" for example !foss@beehaw.org and after a few seconds it should show up and then you can click on it and subscribe.

A web browser, yes, but you should be able to use your sopuli.xyz account just fine. For example, to get to the Jerboa community we're having this discussion in, you would go to the URL https://sopuli.xyz/c/jerboa@lemmy.ml in your web browser. What that does is basically tell sopuli.xyz to show you the community named "jerboa" hosted on the domain (instance) named lemmy.ml. Without the @lemmy.ml, it would look for /c/jerboa on sopuli.xyz, and get a 404 because it isn't hosted there.

If you're signed in to sopuli.xyz on that web browser, you can subscribe to the community from there, and then you would be able to get to it from within Jerboa. My account is with beehaw.org, so if I wanted to do the same, I would go to https://beehaw.org/c/jerboa@lemmy.ml. It's a bit weird, but not that complicated, and it will quickly seem normal once you get used to it.

All that said, one thing I've noticed is if a community from a different instance than the one you're using has 0 posts, it will 404 if you try to go to it from your own instance, and it also won't show up in a search within Jerboa. For example, animanga@lemmy.ml has 0 posts as of this writing, and will 404 if I try to view it from Beehaw or sopuli; it only shows up if I view it directly at lemmy.ml/c/animanga, which doesn't help much since I don't have an account with lemmy.ml.

Use the search from a browser instead, yes