According to the information I've found so far on this topic, JSON Web Tokens fall into the scope of
cryptography and RTC is not a cryptographic library.
But, I did find an
Open Source Delphi Project which seems to have JWT support, so it might help you get started. It looks like that Project is under active development and the author provided his E-Mail address, so you could also
try shooting him an E-Mail if you need help. Or ... you could try contacting one of the Delphi cryptography component vendors like StreamSec or Eldos to ask if they have something ready to be used out-of-the-box.
Best Regards,
Danijel Tkalcec