It could be one of the catalytic converters has come loose internally. You wouldn't be able to see it, but they can make a rattling noise.
Take a rubber mallet and tap on the exhaust to see if you can recreate the sound. I attached a pic of their locations.
Also, make sure the same type of thing hasn't happened in the muffler.
Let me know what you find or if you have other questions.
Take care and God Bless,
Friday, March 12th, 2021 AT 8:21 PM