I'm somewhat confused about the options I'm giving when voting to close a topic.
First I get this dialog:
I choose the middle option with the expectation that I get to choose a proper SE site. But in the next screen I only get this:
How is this supposed to work?
This is functioning as intended. This option only allows migration to a select set of sites that are common migration targets and the publicly available targets must be added by Stack Exchange personnel. It's limited to only a few options as well and those options are only non-beta sites when they are added.
The meta option is there for the community to be able to suggest a question should got to meta.
The reason for the limitation is that the requirements for migration are actually relatively complicated. The question needs to be a good fit for the new site, not be a duplicate and not require clean up to be a good question.
If you see a question that seems like it would be a good candidate for migration, what you can do is flag it as requiring moderator attention and make your case there. Moderators are able to migrate to any site on the Stack Exchange network regardless of any publicly available migration options, so we can still get it to the right place, it just requires a second round of eyes looking at it.
In addition to AJ's answer, the one I'd always recommend is to choose "Other" from your options above - then you get a free text box to explain where you would like it to go.
Once a site graduates, the most popular migration sites are usually added as the defaults.
