In your section " * ## PKI / Certificate Authority (CA)" you point to the pkcs11_engine for certificates with a very generic link to the OpenSC page on git.
I have my doubt that the engine is still part of that source - so it will not be installed when you build OpenSC.
Instead it seems you have to build Libp11 which includes the engine. So you might want to update your documentation - when I am right
PS: Oh, and FreeBSD User need to change the paths given in the description as the engine is installed in a different path