The 5e Ninja subclass has been overhauled – features changed and moved to different levels.
Ninja Combat moved to 11th level, renamed Combat Style with a couple changes and two new options.
No Face merged with Ninja Arts. Some corrections on Ninja Arts. You now get access at 6th level (from 11th) and only get to pick two arts.
New 17th level feature allows better Ninja Art efficiency as well as two more arts and one additional Combat Style.
Opportunist reworked into a new 3rd level feature to keep Ninja damage up with other monk subclasses since Combat Styles mainly add non-damage effects or Flurry of Blow patching.
Proficiencies streamlined. Now ties in to Aronar’s Armory content (hence light flail and scimitar’s removal as well as the ninja weapons section).