Settings/roomname and scroll down. 

The EQ settings can go missing in the app.

If they do not appear under the Sound section in the Arc Ultra’s room settings, force close and reopen the app. You may have to do this a few times before the EQ reappears. Another option is to fully remove the app from your device and reinstall when this issue occurs.

Thank you 

"Check for a firmware update first. If the EQ is still missing, try reinstalling the Sonos app. If the problem persists, definitely contact Sonos support—it might be a bug they need to fix."