Philanemo Mushroom is found under the eaves of houses.
You can purchase Philanemo Mushrooms from Botanist Chloris. The refreshes every 3 days and the items don't change. oou can't see her at night.
Puzzles, Secrets, and Hidden Chests in Liyue
Ragged Records Hidden Quest Guide
Puzzles, Secrets, and Hidden Chests in Dragonspine
Violetgrass Farming Map
Treasure Lost, Treasure Found Quest Guide
How to Farm Character Ascension Materials