So as soon as the ranked was up again, I (foolish me) tried for one game.
Once the champ select was done, the client changed to display "game in progress"... but nothing else happened. The loading screen didn't pop up, at all. It took me a couple of seconds to realize what was happening, so I went through the drill as with the black-screen client crash: ctr+alt+sup the league processes. Differently from before, this time the game itself wasn't there. The moment I closed the client processes, the game process appeared (although only in the task manager). I closed it, reopened the client, and was able to join the match on time.
So, this one is a new flavor of not-connecting after champ select.
The lesson here is, don't play after patches or maintenance, check the boards instead.