Can you add an external fingerprint reader to a MacBook that will work like the built-in reader? I would like to use an external keyboard, mouse, monitor, etc and have my MacBook closed. The only issue is that I can no longer access the fingerprint scanner. Is there a way to use an external one? FYI, I have installed Unlox which is very useful but doesn't cover all cases where a fingerprint can be used.

Yes, I read the similar question but thought this one was different since that one referenced a 10-yr old Macbook that didn't have the Touchbar. And there are ways to solve the problem in that question.
No, there's no external fingerprint reader that works like the built-in reader. The built-in reader is not communicating directly with macOS on the main CPU, instead it communicates with a seperate kernel (still Darwin) running on a secondary ARM CPU.

As there's no way to connect an external fingerprint reader to the secondary ARM CPU, it is simply not possible for 3rd parties to create something that works exactly like the built-in reader and offers the same functionality.