According to Fabrizio Romano (via @iMiaSanMia ), Chelsea will need a straight transfer or a loan with an obligation to buy from Bayern Munich if the Germans want attacker Nicolas Jackson:

Bayern Munich close in on Chelsea striker Nicolas Jackson, Manchester United midfielder Kobbie Mainoo considering leaving Old Trafford, Tottenham face transfer setback with pursuit of Como midfielder Nico Paz.

The agent of Nicolas Jackson says his client could seal an imminent transfer away from Chelsea after being linked with Bayern Munich.