if you mean shoujo as in the genre, where the story was published in a magazine targeted at girls, your best bet is gonna be the classics. anything by CLAMP or the OGs (Ikeda, Hagio, Taniguchi, etc), Sailor Moon, Banana Fish (yes this was published in a magazine targeted at girls aged 12-16, shoujo used to be transgressive for the mere fact that the industry didn't put much stock into what girls were reading until they realized what a major market it was)
if you mean romance manga, I'm not actually sure outside of the fact that nowadays, Josei is a more popular sphere for exploring LGBT themes
Arelyn Is Sick and Tired
It's a shoujo manga, but the duke and another guy, his subordinate called Mehen would go so well together, the MC is the daughter of duke, and she calls mehen mommy hahaha, I don't remember the other name where the MC transmigrates into a bl world tho, but I think it's pretty popular, so maybe search up some key words

Can someone give any recommendations with shoujo plot and shonen ai sub plot? I recently read a manhwa where the daughter has a shoujo plot, and the father had somewhat of shonen ai feels to him and another character. Maybe something like that? I have seen one where the MC transmigrates into bl world, I just need some more ( ;∀;)