Just want to add some side notes: earlier freemangordon updated qyoutube and other stuff; the last fix I found was this.
So maybe there were changes again on youtube's side TLS or something like that but I do not know how to fix it or analyze it... It is just a hint...

Maemish; on Kali image I was never ever concerned about ipv4 and ipv6... Youtube-dl just downloads the video and then you can watch it...
For me it is not a user-friendly option because it is OK when you know what you want to watch exactly... If you just want to surf between videos and watch 1-2 minutes and then click something else then this method just sucks...