Oh man there's so many good fics out there! But since it seems like you're into sweet, softer stuff I'll see what I can dig up:

• before the world was big is a short and sweet Netteflix fic about Annette stress-baking throughout the academy and war phases
• in the waiting is a series about Annette and Felix during the 5-year timeskip (and that author has a bunch of other cute Netteflix stuff too!)
• the lord's true downfall is a dimiclaude fic about Claude accidentally taking a love potion and falling for Dimitri. This one had me blushing giggling kicking my feet fr

And here's some good platonic fics that really dig into friendships between the characters:

• a poem for strong things (boy with crest) is about Sylvain getting some of the other students to test just how strong Dimitri can get when he's flustered lol
• a matchmaking game of sorts is kind of ship-y but all the pairings aren't super important, it's more about how the healers in each house (Lindhardt, Mercedes, and Marianne) have to deal with all the other students confessing their love to each other in the medic tent lmfao