The Filanemo mushrooms in Genshin Impact are used to ascend the characters Barbara, Klee and Mona - 168 mushrooms are needed for each hero.
Usually mushrooms grow under the eaves of houses, but the best place to find them is in the town of Mondsstadt and the Springvale neighborhood, south of Mondstadt. Mushrooms are found on the houses themselves, usually under roofs or on walls.
You can also buy them from the wandering merchant Kloris, 1000 pes per mushroom. The merchant can be found at Petrel Peak.
Cloris walks the Petrel Peak
And he didn't indicate the locations of the merchants on the map, then don't write about them at all !!!! spoiled the mood ...
So they seem to be not difficult to find