The phrase 'except for how' is correct and usable in written English.
It is usually used as an exception to something that has been said previously, to emphasize a point. For example: "Most people find my cooking to be delicious, except for how my cakes tend to be a bit dry."
I'm trying to think about anything except for how high I am.
Three former aides said the takeaway from Charlottesville is the nihilistic notion that nothing matters except for how things play.
Perry's "E.T.," from that same year, needs no explanation, except for how Kanye West ended up appearing on it.
Little distinguishes it from any other shop on the strip except for how long it has been on Fulton, and the woman for which it's named.
It made you wonder what Arsenal had learnt in the last few years, except for how to collapse under the lights, under pressure.
If you knew nothing else about N.F.L. teams except for how well they've played so far this season, this is how you would want to handicap the games.
There was little apocalyptic about the tennis happenings of the weekend, when Serena Williams and Rafael Nadal won the Italian Open, which was completely unsurprising except perhaps for how easily Nadal dispatched the formerly formidable Roger Federer.
Except, maybe, for how to protect the pseudonyms of very famous authors.
For how, except by the merest fiction, can they specify the number and character of the parts which will produce weight?
No. Red Nose Day Actually steered clear of politics, except for saying how sad it was that Piers Morgan was still alive.
Indeed, for such a gregarious person he was strangely quiet about his childhood, except for telling how a man, known as the Major, had given him ballroom dancing lessons.
