How can I generate non-extended keys and Cardano-addresses?

Hello.

With the following command I can easily generate normal (non-extended) signing/verification keys:

#cardano-cli address key-gen --verification-key-file test.vkey --signing-key-file test.skey

The result signing file looks like:
{
“type”: “PaymentSigningKeyShelley_ed25519”,
“description”: “Payment Signing Key”,
“cborHex”: “58205603938b6f6fa9acd09b692126fxxxxxxxx865c81f7ca1ddcb40b5d41xxxxxx”
}

So this is a simple signing key, what I can use PyNaCl library without any problems.

How can I generate similar simple (non extended) signing/verifying keys with Cardano-addresses?

I cannot find any way to generate non-extended keys from menemonic/derivation.

Any advice?

I keep on running into questions like this where users want the functionality in cardano-wallet (namely import/generate from mnemonic) to build (build-raw) transactions using verification-key and signing-key that currently can only be built with cardano-cli.
You should probably open a github ticket or inquire the dev team about this.