Automatic Out-of-Hours Ticket Notification Emails

Hi there! I've posted a few times before but not enough to be an expert about exactly where things go, so if I'm in the wrong spot just let me know!

I work for a company that uses Zendesk Support to keep track of tickets, and we only have a handful of support employees.
We've been tinkering with the systems available to us for quite a while to see if we can get notification emails that normally are sent to Assignees and Followers to send those exact same emails to different employees while one is off-the-clock.

For example (just for clarity) Employee A works 9-5 and gets notification emails on all of the tickets assigned to them. If a customer emails in on a ticket that Employee A is assigned to at 6pm, we'd like that same notification email sent to Employees B and C who are working at 6pm, but not to Employee D who is not working. To be clear we DO NOT need out-of-office responses to customers.

We'd be okay with a system that uses Followers in order to accomplish this, as long as it removes the followers when they're not on the clock, or if the Assignee is on the clock.
We have around 100 tickets at any given time between us, so it puts us in an awkward spot.

We've been opening up the browser and messing around with the API and Javascript trying to accomplish this, but haven't had any traction. I first of course looked into solving this with triggers or automations, but it appears that there's this massive schedule feature that we don't have, and the functionalities in there that existed previously are now gone? I might be mistaken about that.
Regardless, the Schedule seems like WAY more than we need for this super simple schedule-based sending of email notifications.

Is there a way to accomplish this?