According to the article, the FBI has access to:
"User account information like the e-mail address associated with your account, your followers and follows, etc.
All your posts: public, unlisted, followers-only, and direct ("DMs"). Possibly IP addresses associated with your account - IP addresses on Kolektiva.social are logged for 3 days and then deleted, so IP addresses from any logins in the 3 days prior to the database backup date would be included.
A hashed ... version of your password."