Yay, me. I finally figured out what I was doing wrong when I was trying to change the laptop’s screen brightness. Spicctrl is there and works just as it should, but only if you use it correctly. I had to chown to give the file to my username, then decide upon the setting, then give it back to root and set the default. An “aha!” moment–I’d been trying to do it as me, not root, even though I know full well that users don’t have access to system files, only settings that affect that one user. Oops. 🙂