Why are migrants at the Southern Border being flown into U.S. cities, but Cubans are being rejected?

It's because Cubans are fleeing an authoritarian communist regime and that would be "problematic" for everyone over here with a hard on for communism.

If you do come at the southern border be sure to come as a family. They let unaccompanied minors, families, and some adults stay while their court date approaches. Single adults they send packing back home

Facts!

We all know why, Cubans don’t like communism anymore.

So do you mean to suggest that if they still liked Communism they would be accepted as well?

Absolutely, the open southern border does not discriminate but Cubans were warned not to come they would be turned away.