The list of Jakarta EE specifications is available here:
https://jakarta.ee/specifications/. As has already been discussed here, there are a number of implementations for most of these - for example Jersey, RESTEasy and CXF all implement JAX-RS, and Hibernate, EclipseLink and OpenJPA implement JPA. I appreciate that potentially gives you a number of different implementations to evaluate across the specifications that you're consuming (not 1800 though - the website you link to is for example data models). If each specification only had one implementation, it could be argued that it isn't really a specification - just a library. There are a number of Jakarta EE compatible servers:
https://jakarta.ee/compatibility/, and this is in-part down to the availability of a number of different implementations for the various specifications.
From a developer perspective, you shouldn't need to know the deep details of each implementation - just the specification should be enough. If you're developing to the specification, you should be able to move from one implementation to another without too much difficulty.
Hope that helps.