Is that basically means the end of the bare workflow??
No, In EAS both workflows are starting to overlap a bit, but bare workflow will have still important use cases that managed workflow can’t handle. If the only reason for ejecting was adding some third party library then managed workflow on EAS will solve that but in most cases users will still need to use bare workflow.
in order to be able to eject and implement a library using native code.
Technically it would be possible, but EAS Build service is more intended to build app with native dependencies not to develop those native dependencies. You would need to wait 10-20 minutes for every native code change to check if your code even compiled. If you decide to do that I would suggest doing that in bare workflow, it would be a bit simpler this way and when you finish that library you can use it in managed project.