Got a workaround with 2K support's help. (I didn't realize that Shift+Return will do an "end turn" without the requirements for a normal end-of-turn being satisfied, e.g. with no civic selected. That keyboard shortcut doesn't seem to be documented in the options list - I know because I looked before posting this bug report.)
The problem occurred because I completed “Future Civic” and chose to change governments in that same turn, back to one I’d had previously.
As a result my civilization went into anarchy.
Apparently while in anarchy the game will not allow a civic to be selected. I understand that you make no *progress* on the currently selected civic during anarchy, but you can’t even make the selection if you just completed one. (It might not be specific to the “Future Civic”; it’s possible that if you complete *any* civic and use that same turn for a government change which puts you into anarchy, you might get stuck being unable to satisfy the game’s “choose civic” demand.)
So I used Shift+Return to get beyond the anarchy period, and then the game allowed me to choose Future Civic and continue playing.
It would be a good idea for the game to either allow selection of a civic during anarchy (without making any progress, of course) or for the game’s “choose civic” code to detect that the civilization is in anarchy and not make selection of a civic mandatory at that point.
