The Brazilian forward has been stood down as the season draws to its close.
Images said to show all three of United's adidas strips for next season have appeared ahead of any official announcement.
The west London club are reported to be considering the former Hull City manager as they look to reduce expenditure.
Sir Jim Ratcliffe is understood to want the England captain at Old Trafford, according to GiveMeSport.
With their pursuit of Julián Álvarez stalling, Barcelona are exploring alternatives as a post-Lewandowski rebuild takes shape.
The forward's future at Old Trafford appears increasingly untenable as the club charts a course without him.
The Atalanta midfielder, out of contract next summer, had long been associated with a move to Madrid.
