Short bl:
https://www.mangago.me/read-manga/i_wanna_die_before_i_m_30/
Highly explicit manhwa:
https://www.mangago.me/read-manga/him_him_him/
Manhwa I didn't particularly enjoy:
https://www.mangago.me/read-manga/polyamory/
Manga about a woman with a gay husband I think?
iirc the translation on this one isn't great (I'm not caught up on it and I last read it a while ago):
https://www.mangago.me/read-manga/me_my_husband_my_husband_s_boyfriend/
There's also a drama for this one. If you want poly dramas, Sannin Fufu just finished airing today and I think it's probably better poly rep than Watashi to Otto to Otto no Kareshi.
You can also search through the poly tag:
https://www.mangago.me/tag/polyamory/
Like is there any poly manga out there? Can anyone recommend me one