How do I paint with chalkboard paint without it being a chalkboard?

Sure is. You can wax it with either light or dark wax, or you can apply a coat of polyacrylic.

I would imagine any sort of sealer would work to prevent chalk from sticking to it. I would use a polycrylic like this one:

https://amzn.to/2oovDWw

Use chalk paint, it's more durable and same texture. They (rustoleum) make a clear flat finish to seal it with.