E.g. I have some dummy Account Contacts and those are now customer user. I want to provide them only public knowledge article access and don't want them to provide private article access, but issue in here is as they are Customer user they can able to access whole internal knowledge articles.
Are they accessing the articles as authenticated users in an Aura or an LWR site? Or are they accessing the articles as a guest user?
With Aura sites, you can only separate authenticated from guest in terms of which articles can be seen. With LWR you have a little more flexibility.
Depending on your sharing model for Knowledge, you may have different options. Do you know if you're using the Salesforce standard model or the Knowledge data category model?