Harrison suffered a season-ending knee injury against Penn State on Sept. 27.
Jacobs spent six seasons with the Terps from 2013-2018.
Randy White played for the Terps in the 1970s and was a two-time All-American.
Canada served as the Terps' interim head coach after DJ Durkin was placed on administrative leave.
John Donovan was a coach for Maryland for 10 seasons.
Durkin was fired as the Terps' head coach in October 2018.
Among other signings, coach Mike Locksley secured five-star wideout Rakim Jarrett.
The Terps flipped local five-star wide receiver Rakim Jarrett from LSU on Wednesday.
Jarrett is the Terps' first five-star recruit since Damian Prince in 2014.
“He has the characteristics of the great ones,” coach Mike Locksley said.