No! If you have a domain and can do DNS* verification you can get fully functional certificates to use on your internal network.

*Doesn’t have to be DNS, but then you’d need to expose http to the internet for verification.

Hmm. They might. Hadn’t thought of that.

This requires more research. You must buy one - for science! And, I guess, for “science “.

Two dingi don’t make a right. Or something.