Is ONE PIECE episode 955 filler?
Canon No, episode 955 of ONE PIECE is canon.
#955
A New Alliance?! Kaido's Army Gathers!
新たな同盟！？カイドウ軍大集結
Aired 20 Dec 2020
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.