The centos-sb-certs package is required to build the CentOS kernel (via the system-sb-certs alias), so it should be provided in CRB, so that the kernel can be built in plain CS10 mock (as shipped by the Fedora's mock package). In CS9 this package is already shipped in CRB (see https://mirror.stream.centos.org/9-stream/CRB/x86_64/os/Packages/).

Use case that doesn't work:

1. centpkg clone kernel
2. cd kernel
3. git checkout c10s
4. centpkg mockbuild --root centos-stream-10-x86_64

The above fails with:

[...]
No matching package to install: 'centos-sb-certs >= 9.0-23'
[...]
No matching package to install: 'system-sb-certs'
[...]
Not all dependencies satisfied
Error: Some packages could not be found.

Could not execute mockbuild: Failed to execute command.

With C9S the equivalent steps install the dependencies successfully:

1. centpkg clone kernel
2. cd kernel
3. git checkout c9s
4. centpkg mockbuild --root centos-stream-9-x86_64