The solution for this is to run your own CA internally and push out the cert to all the machines. (if you have byod stuff it makes it a little harder but you could still have an internal ca signing only a certain subdomain and get people ot install it)

But that don't protect you from a malicious user hijacking this domain in the next cubicle. Perhaps, if your switches are not properly configured , that the guy in the next cubicle ou do some arp spoofing and https://intranet.yourdomain would be served by a bogus server collecting passwords.

But your users won't notice the difference, because they are used to see the certificate warning on his browser.