Moor
How to Put a Dock on Every Monitor on Your Mac
macOS has one Dock. Apple says that with Displays have separate Spaces on, the Dock is available on all displays, but users in Apple's forums report it moves to one screen at a time rather than staying on two. For a dock on every monitor, use a Dock replacement. In Moor, press Control-Option-E, open Placement and choose All displays. Moor can also make a dock follow your pointer or the active window, or use outer edges only.