I think PSG will be happy letting him go as much as Manchester United will be seeing Harry Maguire leaving them. Or maybe less for Neymar. The fact a player getting many injuries will reduce his playing time and will make it harder to sign him from PSG since there is high risk of injuries..
Manchester United wants Harry Maguire to go as soon as possible since he is underperforming in every United game in which he has appeared. Erik Ten Hag would want to see a change on his team next season. PSG will let Neymar Jr leave because he isn't a consistent player. Every season, he is injured and unable to play until the end of the season. Neymar is one of the most gifted players in football history, but the Brazilian need more time to develop his form after each injury. Perhaps the club decided it was time to let him go since they needed to focus on other players.
Based on the success of specific individuals Manchester United and PSG are considering making some adjustments to their teams. Dissatisfaction with Harry Maguire performances may prompt Manchester United to decide to fire him. It is never easy when a player does not perform well especially on a famous team like United. In a similar vein Neymar Jr uneven availability as a result of persistent ailments may have had an impact on PSG decision to let him leave. Despite Neymar undeniable brilliance his injuries prevent him from making a season long impact consistently. Perhaps PSG believes it is important to concentrate on athletes who can be a more dependable presence on the pitch. It will be intriguing to observe how these prospective moves play out and how the teams adjust to the lineup adjustments.