Rivian has filed a patent for a bike rack that they named the “Integrated Tailgate Cargo System For Automotive Vehicle”.

Basically the rack fits on the tailgate when it's folded down so you don't lost any space in the bed. The design adds special grooves along the tailgate. These grooves could accept wheel mounts (or other securing hardware) that would then bolt in to stay in place.

Wheel Bicycle Bicycle wheel Font Slope

Font Parallel Rectangle Diagram Line art
Font Bicycle part Parallel Circle Art