Generally, I’d look to these:

• https://sdf.org/?faq?BASICS?04
• https://mastodon.sdf.org/about

The rules are not Lemmy-specific that I’ve seen but the overall policies are:

1. Don’t be a dick (no harassment, discrimination, transphobia, hate speech, disinformation, etc).
2. No commercial activity (SDF is both a non-profit and philosophically opposed to spreading the rot of the commercial www - people need spaces that are not about engaging in commerce).