Copy/pasting from another comment I made, hopefully helpful. Written for my instance, but the idea still applies:

In the “All” feed and in the community search, you will see every community that at least one person on this instance has subscribed to.

If you want to subscribe to a community that is not from a blocked instance that nobody has subscribed to yet, you need to follow these steps:

1. Get the full URL of the community (for example, https://lemmy.sdf.org/c/retrocomputing). You can search for communities in the community browser or in lemmy.directory.

2. Open the “Communities” page at the top of the website

3. Paste the full URL into the search, switch all search settings to “All”

4. Wait 5-10 seconds for our instance to pull in the community from that site

5. Click the federated link it gives you (https://sh.itjust.works/c/retrocomputing@lemmy.sdf.org, for example) and subscribe.

That community will now always have the latest posts, comments and vote totals pulled in as soon as the other instance publishes them

EDIT: Should probably mention that as soon as Kbin sorts our their technical difficulties, then you can use this exact approach to pull in Kbin magazines (https://kbin.social/m/cs, for example)