I remember one carbon frame with a belt opening, Rose Bikes had the CPTL for a few months.
Thanks for the recommendation on the titanium frames, gotta contact them.

Hey guys,
I'm searching for a frame to build my daily bike from.
I want fender- and rack mounting points and compatibility with rohloff and gates carbon drive, material of the frame is secondary although I'd prefer either carbon or titanium.
At least 40mm tires, preferably more.
Does anyone have an idea if this kind of frame exists?

Cheers!

Mondince supposedly are also planning a bike with 57mm clearance

https://www.ti-product.com/titanium-cargo-bike-frame-with-pinion-gear-box.html

Found this a few days ago and meant to ask if anyone has experience.

Sounds like a frame I want without costing as much as a Fara Gr.4

Hope it gets frame storage.