What year(s) did all this happen?  If 2022, has that return already been filed?

Form 8606 can be filed as a standalone by someone not required to file a 1040.  But I think if a 1040 is filed, it has to go as an attachment.  If 2022 is involved here, it's not too late to do a  superseding return, although that might be more work than needed.