Are there any bl manhwa that end with a throuple?

Yes pretty much.
I Wanna Die Before I'm 30
https://www.mangago.zone/read-manga/i_wanna_die_before_i_m_30/

There's No Way This Is Fate.
https://www.mangago.zone/read-manga/there_s_no_way_this_is_fate/

There's No Way This Is Fate. -Newlyweds Arc-
https://www.mangago.zone/read-manga/there_s_no_way_this_is_fate_newlyweds_arc/

Help Me, Teacher.
https://www.mangago.zone/read-manga/help_me_teacher/

A Dead Crow's Stare Webtoon
https://www.mangago.zone/read-manga/a_dead_crow_s_stare/
Bad writing tho, I didn't like it

Canis
https://www.mangago.zone/read-manga/canis/

Lick Me, Like Me
https://www.mangago.zone/read-manga/lick_me_like_me/

Bed for Three.
https://www.mangago.zone/read-manga/one_two_three_1/

Myungtae, You Little Rascal!
https://www.mangago.zone/read-manga/myungtae_you_little_rascal/

Jealousy (Cheonghu)
https://www.mangago.zone/read-manga/jealousy_1/

Love Debugging.
https://www.mangago.zone/read-manga/love_debugging/

Yum yes thanks for the new reads

You're welcome sweetie ٩(๑❛ᴗ❛๑)۶