So far, Osimhen's future is certain to remain at Napoli because no team is serious about asking for him at a price that is too high. It is true that there are teams that want Osimhen's services, including several teams from the EPL, but so far there has been no concrete decision regarding this desire. That way, it is certain that Osimhen will stay at Napoli and Osimhen will even play in pre-season.
I don't think Victor Osimhen is comfortable playing at Napoli anymore but for the fact that no team have been able to sign him implies that he's left with no option than to stay at Napoli possibly next season other clubs may come looking for him. Last season, Osimhen was not that consistent as he used to be due to some injuries the Nigerian striker suffered but he is still a tactical player that most teams will want to join their squad. He should just make up his mind at Napoli and make quality contributions to the team in that way he will become more visible for other clubs to find him worthy of signing, I'm not saying that he is not being impressive but for him to gain more recognition by other big teams that's the area am talking of.
Even though Antonio Conte himself is reportedly willing to let Osimhen go to another team, perhaps it is because the striker does not suit his strategy that he insists on bringing in Lukaku.
I don't think Antonio Conte has any problem with Victor Osimhen so even if he brings in Romelu Lukaku it's still not a bad decision but I prefer Victor Osimhen to Lukaku because Osimhen is more of a tactical player than Lukaku.