Ellis was the second Nittany Lion to sign a UDFA after Curtis Jacobs signed with Kansas City.
Jacobs will join Hunter Nourzad, who was a fifth-round selection, with the Chiefs.
A poor showing against Ohio State started a downward trend for the once-first-round projection.
Hardy became the seventh Penn State defensive back to hear his name called.
Nourzad was the second Penn State center drafted in the last two years.
Johnson joins Mike Gesicki, Brenton Strange, and Pat Freiermuth as former Penn State tight ends currently in the NFL.