On the following question:
> what is the d-i solution here?
I believe for that you need to pass "debian-installer/allow_unauthenticated=true" to the installer cmdline, and then it will accept such insecure apt mirror during the installation process.
On the following question:
> what is the d-i solution here?
I believe for that you need to pass "debian- installer/ allow_unauthent icated= true" to the installer cmdline, and then it will accept such insecure apt mirror during the installation process.