Another option is Reddit. There are specific subreddits dedicated to Komi - san where fans might share their own fanfics or recommend good ones they've read. It's a great community to interact with other fans as well while looking for good fanfic.
One popular theme is Komi-san's attempts at making more friends. Another could be Komi-san's experiences in different social situations outside of school. Also, fanfics might focus on the relationship between Komi-san and Tadano developing further in various scenarios.