Clunking sounds are hard to diagnose from a video
But, it "could" be:
Broken or loose engine or transmission mounts,
tail shaft couplings, centre bearing or uni joints, diff slap, suspension bushings, exhaust hangers, or even a clearance issue somewhere with the exhaust
Take someone for a drive with all the windows down and ask them where they think the sound is coming from, do this going forward, and then reverse, then have them stand outside the car and listen
Once you dial in where the noise is coming from you can jack up the car and put it on stands and remove the wheels to inspect the suspension, tail shaft, drive shafts and CV joints for play or damage, inspect everything and give everything a good shake and optic nerve
You can use a pry bar on the bushings to look for play
If this isn't possible because you don't have the equipment, take it to a "good" workshop and get them to diagnose the issue
Importantly, don't keep driving the car until you have diagnosed the issue as you can make things much worse