Technically, anything is actionable - the action can be to do research, have a discussion, set it to Feedback needed, reject the issue due to lack of feedback or because we think it can't reasonably be done.Regarding the no version state: My opinion is that this should be used for issues that are not actionable, not because of external issues (need prerequisites done, needs 1.0 first etc.), but because of issues with the issue itself: insufficient information to categorise it, triage not happened yet or still in progress and so on.
Every other issue should have a version number assigned to it, because that means it will appear somewhere on the roadmap and given the right circumstances a developer can pick it up.
I'm not opposed to having a list of 'ready to code' issues somewhere, but I don't think versions/milestones are the right way to do it. It would be nice if we had tags.