I have a
Flyxii FE-711 that is pretty close in looks, geometry, and specs of a Stache 29+. Actually bought it because I couldn't find a carbon Stache frame at the start of 2020.
I currently have it built with a set of boost Duroc 50s, alternate between 29x3.0 Maxxis DHF/DHRII and 29x3.0 Vittoria Cannoli, 130mm Rockshox Yari, and a full SLX 7100 groupset and brakes. Pretty close to stock Trek kit and there is a ton of room in the rear for an even larger volume tire. The headtube on the FE-711 is probably a bit longer, but other than that most should just transfer right over.
I tried to get a few other 29+ frames from from Aliexpress but they either weren't available or only in smaller sizes in stock from retired molds. Flyxii quality can be questionable, if you do decide to get one make sure to inspect it thoroughly.