any school life bl recommendations that has the popular x loner or whatever trope?

Theres a few but some arent the exact trope you listed! Some have smut in them if you dont mind ^^

Popular x Loner:
https://www.mangago.zone/read-manga/hetakuso_love_step/

https://www.mangago.zone/read-manga/oreshika_shiranai_karada/

Not exactly word for word the trope but a personal favorite:
https://www.mangago.zone/read-manga/thoroughbred_wa_nabikanai/

Not exactly popular x loner but its similar, more like bad student x nobody with a twist:
https://www.mangago.zone/read-manga/bending_the_spoon/

College one:
https://www.mangago.zone/read-manga/love_works_in_mysterious_ways/

Long but super good enemies to lovers:
https://www.mangago.zone/read-manga/semantic_error/

A pretty long one where its enemies to lovers popular prince x disliked student
https://www.mangago.zone/read-manga/the_royal_prince_s_first_love/

Misunderstanding:
https://www.mangago.zone/read-manga/kimi_towa_gokai_kara_hajimarimashitaga/