Yes his right foot is his weak foot, and he uses it far more than often than anyone else in the team use their weak foot except for Varane (who I just found is even higher). It's obvious to the eyes, and FBref even has stats which show it.
Percentage of passes played using their weak foot:
Varane - 41%
Fred - 29%
Greenwood - 23%
Ronaldo - 16%
Lindelof - 16%
Maguire - 14%
Matic - 14%
Pogba - 12%
McTominay - 7%
If you want actual hard numbers compared to the others in midfield (per 90 minutes):
Fred averages 17.35 passes with his right foot
Matic averages 9.9 passes with his right foot
Pogba averages 5.73 passes with his left foot
McTominay averages 2.26 passes with his left foot
I honestly don't understand why the 'Fred only passes with his left foot' thing came along. There's not many players around who make more passes with their weak foot, and I never hear these complaints about our other midfielders (especially McTominay who actually is incredibly one footed).