On team-managed (formerly next-gen) projects, the Release feature when enabled shows "Fix versions" in all built-in issue types like Bug, Story, Task, etc.

But when we create a new Issue type like "Theme" in below sample screenshot, the Fix versions field is not available to use.

We are also unable to create a new field of "Versions" type

Workaround:

To workaround this issue, go to Project Settings >> Features, disable the Releases feature, refresh the page, and then enable the feature again. This should display the Fix Version field for all issue types.