I would need a script that ignores all the lines at a specific time every day.

Therefore, every single line on #channel would be ignored from, say, 9pm to 9.05pm.

Would that be at all possible?

/help /ignore
/help /timer

//.timerignore 21:00 1 1 .ignore -u3000 *!*@*

in aliases
/9pm .timerignore 21:00 1 1 .ignore -u3000 *!*@*

or maybe in remotes:
on *:start: timer9PM_ignore 21:00 1 1 .ignore -u3000 *!*@*

I'd change the 3000 to 300 if you want it for only 5 minutes. 3000 would be 50 minutes.

Using *!*@* all the channels I'm on are ignored, which obviously is not good.

How can I specify a certain channel without affecting the other ones?

Thanks for your help, at least I'm getting somewhere bit by bit.

you can set a timer to moferate that channel (and deop/devoice everyone)
you could set a %var with a timer .timerignore 21:00 1 1 set -u300 %ignore 1
on ^*:text:*:#channelname:{
if (%ignore) { haltdef }
}

something along these lines should work