Reports state that the Cameroon international will earn a higher salary at Trabzonspor, who will also pay bonuses and a signing-on fee.
Amorim has opted to start Turkish goalkeeper Altay Bayindir ahead of Onana in the Premier League so far this term despite a series of shaky performances, with veteran Tom Heaton also still at the club.
Onana’s imminent departure means Amorim will have to decide whether to stick with Bayindir, whose mistake nearly cost United a [first win of the season against newly-promoted Burnley](/sport/football/man-utd-burnley-result-premier-league-b1245206.html) before the international break, or hand Lammens his debut at the Etihad Stadium in Sunday’s Manchester derby.