Is ONE PIECE episode 758 filler?
Canon No, episode 758 of ONE PIECE is canon.
#758
The King of the Day! Duke Dogstorm Appears!
昼の王 イヌアラシ公爵登場!
Aired 2 Oct 2016
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.