Hello there !!! I am glad I have found this post because I am a fan of polyamorous trope and healthy threesome, and i haven't read 3 of the titles you mentionned !!! :-) so yay!!!!
Here is my reading list with all the BL threesomes that I find good to reallllly good.
Not always '' poly in the sense of wanting to be a trouple '' they often are enthousiastic FWB :-D that's what I like. That's the spirit.
https://www.mangago.zone/home/mangalist/2345830/
https://www.mangago.zone/read-manga/futarijime_underdog/
There’s a “there’s no way this is fate: newlyweds arc” just in case u didn’t know: https://www.mangago.zone/read-manga/there_s_no_way_this_is_fate_newlyweds_arc/
https://www.mangago.zone/read-manga/aishitagari_w_darling/
https://www.mangago.zone/read-manga/trick_turned_into_a_threesome_with_the_tachibana_brothers/
https://www.mangago.zone/read-manga/itsumo_3nin_issho_dene/
Looking for healthy threesome manhwa/manhua/manga. Or just like something acceptable haha. Things I've read are
•There's no way this is fate
•I wanna die before I'm 30
•Nureturu 3P
•I'm being loved by beastmen in this life
Yeah something of that sort.