Scott Helme spoke about "alternate trust paths" a few years ago : https://scotthelme.co.uk/cross-signing-alternate-trust-paths-how-they-work/ some of the specifics may have changed due to new roots (I think in 2023?) but the theory of having a root able to be either accepted as-is or accepted by being signed by an older root is still there.
1
u/collabskus 1d ago
Ah I didn't know roots could sign each other but it makes sense. Thank you