I use my Mac as a headless server to run LLMs, and never even start a desktop session so it always stays at pre-login state without any applications running. Even so, I never saw it using less than 2G in htop when logged via SSH.
I have similar issues with my ultra. Have put it on a laptop, but my desk Setup with my multiple desktop computers is usb-c video based ( kind of a poor man’s kvm) , and asahi doesn’t do usb-c video yet