@nikofraser: “my current frame (transition transam) is. my wheels and fork are non boost so would be ideal to just put on a new frame. That’s why I’m asking what’s out there”
2015 is not a modern frame. Nothing was Boost at that point save maybe some Trek bikes (they invented it). If you are dead set (you should not be, but more on that in a second) on non-Boost then you’ll be buying used. A fantastic used hardtail that would be non-boost would be a Kona Honzo through ’15. Good luck finding one as they are coveted. Honestly your best bet is to buy a Boost hardtail frame, get a $20 conversion kit and ride on.