Fantastic Four wasn't the first. Marvel has a long history of comics, and several series came before it. Different characters and storylines were introduced earlier that contributed to the Marvel universe's foundation.
The Black Panther comic has its own unique fictional universe and narrative that is not related to the Black Panther Group. The comic's creation was based on comic book concepts and storytelling rather than any direct connection to the group.
The Legend of Black Panther is an audio novel that can be listened to for free. However, the search results did not provide clear information on which platform could be listened to for free. Therefore, I don't know the specific platform for free listening to books.