Thanks. I finally figured that out. I just somehow had not heard of them.

I haven't had a chance to do more than unbox it, weight it, and look at it, and begin the process of agonizing about every part.

I started a separate thread about what drivetrain to use: Di2 options for a gravel bike?

I've got some Di2 shifters/brakes that I will probably use in the build, and they work with road, grx and mountain (all 11-speed) derailleurs, which is a plus.

My wife has started going down the wheel rabbit hole.