I’ve gone through the same journey, wanting a lightweight SS CX. There aren’t many out there. Other than the Pinnacle, there only seems to be the Niner RLT. Even getting a cheap frame (several older models at topfun.com), you’re still looking at £1.5k for a SS build.
I’ve ended up with a secondhand Genesis Day One Decade. Put some nicer wheels on it, and it’s very close to 10kg’s. No EBB (sliding drop-outs), but will take 40mm tyres, which I think is essential. Also don’t rule out TRP Spyres mechanical discs – I rate them higher than the SRAM CX1 hydro’s I’ve had previously.
Also thought about fitting an EBB to a Boardman and the like, but never seen it done.
Nick