Less smart electric front door key turning lock?

Hello interwebz!

I am looking for a non-invasive front door key turning lock addon like https://nuki.io without too much brain. I'd rather run the brain myself in a way I can trust.

 The invasive version that requires changing the lock is easy to find. The non-invasive one, not so much...

Any hints?

Should have examined the proposed tender...

... for a content management system for the city government more closely. Even if I was only involved a teeny weeny bit.

Not just the public facing part should be W3C compliant. The backend should be web enabled too, not just an ActiveX enabled Microsoft Internet Explorer application.

I saw the W3C part and thought the city sysadmin knew what he was doing. Pity...