The news comes fresh from United’s disappointing 2-1 home loss to Brighton and Hove Albion to start the new Premier League season under new manager Erik ten Hag on Sunday.
The Red Devils are also set to miss out on Salzburg’s 19-year-old striker Benjamin Sesko who is expected to join RB Leipzig.
But United are close to confirming a deal for Rabiot, with personal terms to be negotiated.
The 27-year-old French midfielder is in the final year of his contract in Turin and has slipped out of favour.
Rabiot, who has 29 caps for France, is seen as an alternative to de Jong.
Arnautovic, who turned 33 in April, looms as an interesting signing for United having plied his trade in the Premier League previously with Stoke City and West Ham United.
The Austrian forward is currently with Bologna where he netted 14 times in Serie A last term. The Rossoblu are eager to retain him but United are likely to ramp up their initial bid of nine million euros.
Elsewhere, Everton have completed a season-long loan for Wolverhampton defender Connor Coady.
Wolves landed Portugal international Goncalo Guedes from Valencia on a five-year deal and Timo Werner is set to re-join RB Leipzig permanently from Chelsea according to ESPN.
Borussia Dortmund have completed a deal for FC Koln’s Anthony Modeste on a one-year contract as cover for Sebastian Haller.