You could use multiple schedules to achieve this with a dummy user or default user to accept all incidents outside of your requested Support Hours.
If you want to use with this just the built-in Support hours, one workaround, I’ll agree odd, is to change the timezone your Support hours user to be 8 hours ahead of your actual timezone and have the schedule on-call from midnight Monday to 00:00 Saturday in your timezone -8 hours.
The easiest example is if your timezone is UTC+00:00, you would change your timezone to UTC-08:00 and set the time from 00:00 Monday to 00:00 Saturday. If I lived in New York using EST time (UTC-5:00), I would set my timezone in the Service Support Hours to Sydney (UTC+11:00) which is the complement of UTC-13 but select my days from Tuesday 00:00 to Sunday 0:00 as that’s the equivalent of Monday 8am EST to Saturday 8am EST.
Hope this helps!