Salsa Woodsmoke and Timberjack will both take 29 and 27.5+ (Woodsmoke will also take 29+). Pretty sure these can run a belt drive with the Alternator dropouts, but you might want to verify. Otherwise, I think it ticks all your boxes.
I have an El Mariachi which I run both 29er and 27.5+ with a rigid fork. I love it!
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