The problem you’re running into is that your home instance, lemmy.sdf.org, blocks lemmy.world. You cannot meaningfully participate in any community on Lemmy.world because of this.

I’m not familiar with rainy.place (and I’m not 100% on how kbin federates with Lemmy), but presumably they federate with Lemmy.world. if you have a second account on there (or any server that federates with lemmy.world, which is most of them), then you can access that community.