Signing an unsigned apt repository is about three gpg commands though. I don't see how this kind of thing requires a whole separate product.

Yeah, solving this locally for one repository definitely isn't that hard at all. Most of the features we're building become useful when you're trying to build CI integrations for a larger team while also complying with enterprise security requirements (e.g. audit logging, HSM key protections, etc.).

> when we tried to use them in production at scale

Debian and Ubuntu have been using them in production and "at scale" for decades. What are the "sharp edges" that you're trying to solve?

That's true! The Debian and Ubuntu folks are also experts at this. In our experience, the sharp edges generally affect teams that don't have a lot of in-house expertise in this, and where release engineering is not a core engineering competency that they want to invest in.