I've used
https://smallstep.com/docs/step-ca/ as a CA internally, works well.
What I'd want is an internal CA, like step-ca, but have the certificates signed by a "real" CA, so I don't have to distribute my own root CA certificate.
The dream would truly be an internal CA backed by a publicly trusted subordinate cert (limited to the domain you control). But afaik that can’t happen until the Name Constraint Extension is enforced by “all” clients.