When I joined lemmy, I had to join a few different instances before I realized that:
Some instances didn't allow you to create new communities
Some instances were setup with an allowlist so that you couldn't subscribe/participate with communities on (most) other instances
Some instances disabled important features like downvotes
Some instances have profanity filters or don't allow NSFW content
I couldn't find an easy way to see how each instance was configured, so I used lemmy-stats-crawler and GitHub actions to discover all the Lemmy Instances, query their API, and dump the information into a data table for quick at-a-glance comparison.
I hope this helps others with a smooth migration to lemmy. Enjoy :)
The new user registration doesn't map to the recommended setting of admin approval only. There have been massive spam account registrations waves in the past and if you can't monitor your instance 24/7 this is the only way to prevent having your instance blocked because of that.