Okujima Hiromasa, Takahashi Hidebu, Est Em, Okadaya Tetuzoh, Asada Nemui, Totempole, Kajimoto Reika, Mentaiko (geicomi dj mangaka influenced by famous shounen/seinen stories), Iwasawa Midori, KOIKE Sadaji, ARAI Niboshiko, etc (the space here is limited, so no more creator names)
Also: https://www.reddit.com/r/Animesuggest/comments/17vufpd/are_there_any_shounen_manga_with_bl/?rdt=44199&onetap_auto=true
A very good list from RoseMary: https://www.mangago.me/home/mangalist/226060/?filt
yandere/yandere-adjacent characters: numero tres!
a mix of shoujo, platonic, and BL/GL content.
if you want more, check out part 1 & 2 of this list!
-pt 1: https://www.mangago.me/home/mangalist/1674723/
-pt 2: https://www.mangago.me/home/mangalist/1904522/