Which lemmy instances were you on? It could be you were on smaller instances? Kbin.social is a large instance, so most of the forums are already added there. They can improve by making the UI more clear hopefully in the future, but for the smaller instances, you have to do a search for the link of the forum you want, then subscribe to it. Thats the only way it becomes searchable on the instance. Since kbin is working for you, stay on kbin. I’m using kbin.social too and a small instance called lemmy.studio. If you have more questions about adding the community/magazine, make sure to ask :)

What kind of content do you mean is missing?

On kbin.social, a lot of communities should be available since it’s a big server. Which ones are you trying to find?

thanks for the list of the kbin instances! Hopefully we can migrate our accounts someday. Joining kbin.social at first has been helpful to me to not have to go through that growing pain of not being able to see many communities/magazines