The short answer is that if you want to make that decision yourself, you’ll have to start your own instance. There’s a lot of unsavory things on the fediverse that most of us don’t want anything to do with.

You might find a few, but it’s not really possible long term. Either you block instances that are run by fascists or child abusers, or you get blocked by instances for allowing that on your server.

https://github.com/maltfield/awesome-lemmy-instances

There are plenty, I use lemmy.sdf.org

At this point, you might find some small instances that fit that description, but as things settle down, you’ll find that what you’re looking for is impossible.

For example, I’m an admin of a trans and queer centric lemmy instance. My first and foremost goal is giving that community a safe space, in which they can exist with their guard down at least a little, where they know that they don’t have to deal with endless bigots and trolls trying to undermine their right to exist.

So, the moment I see an instance that actively chooses not to block any other instance, even if they’re full of bigots, then I am going to defederate both instances, because otherwise, I’m going to end up trying to deal with endless waves of hate from both sources.

The instance I’m on was not blocking anyone and I’d not seen where anyone was blocking them. However, there’s been a recent influx of instances having a large number of inactive accounts, maybe setting up for some kind of bot invasion. It unnerved the admins and now many are blocking instances that look like bot farms. My instance is now blocking a number of them only for that reason.

Most instances are not blocking other instances for content. Beehaw is the one instance I’m aware of that does block a lot of other instances for content. The others seem to do it much more sparingly, if at all.

As a user you’ll need to check the home instance of your communities. Go to that instance and reference the Instances link bottom of the page. Check your login instance is not blocked there. If it is and you really want to participate in that community, you need to sign up with an instance that’s not blocked.

For example my login instance is lemm.ee. There are some communities I subscribe to on beehaw.org. I go to beehaw.org and select the instances link at the bottom of the page. There I can see that that lemm.ee appears under the Linked Instances column and not the Blocked Instances column.