According to the latest report from Mundo Deportivo, De Jong is still recovering from his injury and is expected to make a full recovery by late October.

According to reports, sources within the coaching staff revealed that the next step in assessing De Jong's injury will take place after the upcoming international break. The international break begins on September 21 and continues until the league returns on October 10 or 11. De Jong plans to use this club competition break to carry out the final strengthening phase of the conservative treatment approach he has chosen.
In this way, he hopes to fully integrate back into the team when he returns to Barcelona training with his national team teammates on October 8. Of course, this depends on him feeling well and no longer experiencing any discomfort in the ligament of his right knee. It is worth noting that Frenkie needs to regain a minimum level of match fitness before returning.
The issue is that after the international break, Barcelona will face a series of strong opponents (Getafe, Galatasaray, Real Betis, Paris Saint-Germain, as well as the El Clasico on October 25), which requires Barcelona players to maintain their best physical condition.
Therefore, Flick will also have an important say regarding De Jong's health condition. At present, De Jong is performing straight-line running exercises on the pitch, but he has not yet started ball training or physical contact with other players. As a result, he still needs to complete several stages of conservative treatment.