Correct, though to be pedantic anyone can be a CA- you just generate a cert with the right bits to say it’s a ca certificate and then use it to sign any other certificate you want.

But the only devices that will consider your signature worth anything are ones you also install your ca certificate on. So it’s useful and common in internal networks but isn’t really what is being asked here.

The hard part is getting in the root CA store of operating systems and browsers. As far as I know they are all maintained independently with their own requirements.

it’s typically up to the distribution to configure things like that, and many Linux distributions do come in both server and desktop or workstation variants like Ubuntu desktop vs Ubuntu server, or RHEL server vs RHEL Workstation

I can’t say how well they tune these things as I haven’t ran them personally, but they do exist.