Sometimes, on StackOverflow site, I encounter a question that I think should be on Unix & Linux site. My problem is that I am not able to signal it.
I noticed that I can, on StackOverflow, flag a question as offtopic and then choose between 5 sites, but I haven't found any way to move it to this one.
Does anyone know if and how this is possible ?
As Mat commented, sites are only allowed to have 5 migration paths. Moderators can migrate anywhere, and we do get a decent number of migrations from SO (about one per day), so at one point we looked into replacing one of the migration paths SO already has, but were told it's extremely unlikely. As this meta post and mattdm said, you can flag the post for moderator attention and say which site it should be on, and they'll move it for you
It would be nice if there were such a migration path. But in the meantime, you can use the "other" flag option and leave a comment for the moderators explaining why you think it should be moved.
