Eldritch Osiris Games has posted a free archetype (plus a child archetype!) on their patreon: The Terror Knight, and the Knight Terror.

Patreon:

https://www.patreon.com/posts/terror-knight-v1-131087852

Reddit Post:

https://www.reddit.com/r/Pathfinder2e/comments/1l7dc3v/nightmare_v_15_terror_knight_revisited_rebalanced/