The lobby screen opens the dashboard at eight and closes it at six

The screen in the lobby shows the ops dashboard. Someone walks over with a keyboard when it wants a login, and nobody turns it off at night.

Put the browser in a container instead. /start?browser_id=0&showBrowser=true&display=1 launches a headful Chromium on the container's display :1; the lobby's thin client shows display-1?readonly=true&toolbar=false in one full-screen tab. A cron entry at 08:00 calls /browse?url= with the dashboard. Another at 18:00 lists /tabs and sends POST /tab/close. When the dashboard logs out, the same cron re-runs the login through /eval.

The thin client never runs anything but a tab. The browser it shows lives on a server and keeps office hours, because a cron entry gives it some.

Signage software is a scheduler wrapped around a browser. You already have both.