Confused about official adobe spectrum icons source, any advice?

Hi everyone,

I’m a bit confused about where we’re supposed to get our official Spectrum icons from. I found the Spectrum design icons here: Spectrum Icons, but it says clearly, “These icons are only to be used for design. When engineering your product, you can find the icon implementations in A4U,” yet the provided link to “A4U” is broken.

I also came across these sources:

Does anyone know the official process or the correct, up-to-date source we should use for implementation?

Thanks in advance for your help!