How are you defining Manchuria? Do you mean Inner Manchuria, the part that falls within the PRC's border? Or do you mean Greater Manchuria (Inner + Outer), in which case Russia is currently on said land (occupying?). There are a great many peoples throughout history that were on the land, but whether you want to call it occupation or not is another matter.

• The Khitan (aka Liao Dynasty) were from the western part of Manchuria but expanded their borders.

• The Jurchen (Jin Dynasty, ancestors of Manchus) were further east, but also expanded their borders and toppled the Liao and Northern Song (Han Chinese).

• The Mongols further conquered the area a bit later with what became the Yuan Dynasty.

• Han Chinese as the Ming Dynasty after that.

• Manchurians who took over after the Ming, starting the Qing Dynasty.

• As the Qing weakened later on, the Japanese and Russians moved in

• Then finally the Communists of the PRC took over after the Japanese left, though not without significant Nationalist KMT presence during the Civil War.

Keep in mind this doesn't include smaller groups that were in the area, who may have had differing senses of who was the occupier and whose land it really was. For example if Sakhalin is included in our definition of Manchuria, then we have the Ainu, Oroks and Nivkhs as indigenous peoples. I'm sure there are more that have been lost to history.

edit: formatting