This repo will focus on .NET core (3.1 and later) code that can be used to create and use self-issued IDs. [https://bitbucket.org/openid/connect/src/master/SIOP/draft-jones-self_issued_identifier.md] is the OpenID draft proposal. The following Repo shows an example of a naked (no reverse proxy) 3.1 netcore microservice provinding an API.
Reference also the repro at https://github.com/dotnet/orleans - a cross-platform framework for building robust, scalable distributed applications