Gravel build cantilever frame

[Triskelion]

Looking for a frameset that'll take 700c with up to 50mm tyres. I'll probably end up closer to 40mm tyres but would like the option.
I'm looking at cantilever brakes to keep the weight down. I've got a spare set of rim brake wheels that would do.
I'm thinking something along the lines of cyclocross plus.
Aiming for under 8kg complete build while spending as little as possiable. Apart from wheels, i've already got a 6800 groupset that I might put on it.
Are there any hidden jems of an alloy hybrid frame worth looking at? Something like a trek fx or specialized sirrus possiably

[jemima]

I think the earliest 700x2.0/2.2 Euro alu beachracer drop/flatbar frames [carbon fork] were canti frame and fork. Seen pics of them with those big Magura calipers.

Steel, there's the 700x50 BlackMtnCycles Monstercross canti frameset available, but you'd have to go stupid weightweenie to hit 8kg complete.