Try Mo Dao Zu Shi?
https://www.mangago.zone/read-manga/mo_dao_zu_shi_novel/
Read these two in this specific order, tho not a sequel they're kinda connected, also don't be put off by the art at the start, it changes for the better in just a few chapters :
Song of Reverberation
https://www.mangago.zone/read-manga/song_of_reverberation/
The Promise
https://www.mangago.zone/read-manga/the_promise/
as far as i remember most of the bls I've included in this list have green flag mls coz I don't read bls with red flags lol
https://www.mangago.zone/home/mangalist/2924996/
finding a bl manhwa with good plot (and preferably a green top & bot) and good/pretty artstyle (≧∀≦) every time i read a bl manhwa that has a good artstyle it always have a super bad plot or the male lead is such a red flag(⊙…⊙ )