Here's a question: can you use Magic Jar against creatures who have had their creature-type changed into "humanoid"?
For example, using the 'Mask' option of Nystul's Magic Aura on a dragon to change it's aura into a 'humanoid'; the spell says: "You change the way the target appears to spells and magical effects that detect creature types such as a Paladin's Divine Sense and the Symbol spell."
Symbol is obviously not a Divination spell, and neither is Magic Jar (and Divine Sense isn't even a spell), so presumably they would be tricked in similar fashion - but even if Magic Jar were tricked in this way, would/should the spell continue as normal (with you in the dragon body, for this example)?
Also, True Polymorph can turn our dragon into a humanoid, so could this trick also work?
just to get logistics out of the way, a wish-magic jar could allow for a quick transition and our dragon may already have burned through their legendary resistances and has been feebleminded for maximum effect. BUT let's assume that, with the logistics taken care of, only the magical say-so stands in the way...so, could this trick work?