Hey, this is Better Snowy Biomes, a project aiming to improve the vanilla snowy biomes.
Check out the edits of Better Snowy Biomes for vanilla leaves (and other things in the future):
Tectonic: Put the fabric mods over Tectonic in the datapack section when generating a world.
Quilt: You need QSL, otherwise it won't work.
Terralith datapack: Better Snowy Terralith
Snow under trees; Snowy Leaves 
Tectonic Support 
Smooth Snow: Inspired by Terralith; made with own code 
