I had my work GMail set to notify only between 0800 (so I could check for a "don't come in" message) and 1700 Mon-Fri. Of course, it didn't account for holidays / sick leave etc, but it was good at prevent me from panic checking every ping.
I wish that was a feature on modern Gmail. Or, indeed, WhatsApp and Signal. You can manually mute, but there's no way to silence specific notifications at specific times.
Regardless, employees shouldn't be expecting employees to be on-call without compensation. But users also need ways to manage this themselves.