The relevant rule is screenshotted below as well. To be clear, this is something we have just clarified to cover this situation as well as situations in the past with the character Ouma from Danganronpa.
We don't normally announce our instance blocks, but we felt we should let our users know that we will be silencing https://lesbiab.space/ and eventually suspending. We were made aware of their rule against he/him lesbians, which is incompatible with our rules and blatantly transphobic and homophobic.
We know that many of our users have good mutuals and alts there and we wanted to give them a chance to learn about this, as it seems like this rule was unknown to most of you.