Ubuntu anti-climax
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TL;DR: no, it doesn’t really work all that well.
The disconcerting “snow” has returned, pretty much consistently. And there’s some weird flickering occasionally, possibly related to occlusion by a translucent window.
Bah, humbug. There’s nothing I can do in the short term except live with it. And I’m really not sure what to do about it in the long(er) term.
Update: I gave up.