Switch to System.Text.Json instead of Newtonsoft.Json?

[frogcrush]

System.Text.Json requires no external dependencies on most platforms and appears to be typically preferred now over NJ.

[2ynn]

Thanks @frogcrush for rightfully pointing this out.
As it stands, System.Text.Json cannot be easily used as a drop-in replacement for Newtonsoft.Json because we rely on features like NullValueHandling and MissingMemberHandling for specific cases, such as undiscriminated union deserialization.
We have started evaluating the necessary steps to migrate and will keep you updated as our roadmap becomes clearer on this issue.