This affects Company-Managed and Team managed projects as best I can tell.
I have several epics in a Done status (literally, status = "Done"), and Resolution = "Done", and all child tasks are in a Done statusCategory. I have "Show closed epics" unticked, and yet our old, long finished with epics still appear when using the Epic Link field on an issue. It's just noise. It makes selecting the right harder, and selecting the wrong epic a definite likelihood, which of course messes with planning and clarity.
The project the epics live in are often different to the project the issue lives in, so does not appear in the Epics list in the project's scrum board, and honestly, that shouldn't matter because many teams use Kanban boards instead, which don't have that thin Epic's list.
This is a Jira bug and/or there's a secret that Atlassian need to share with everyone to stop Done epics appearing in the Epic Link field of task level issues. Atlassian have a large team and must have thousands of Done epics. How do they do it? What's the trick? Is there one?