Code:
<script>
win2=window.open("https://www.StayTheFuckHomeYouFuckingMorron.com")
win2.blur()
window.focus()
</script>
It pops one time every 24 hours or so, not sure, but this one I use since forever,
just add the code INTO a widget ( HTML widget you can add it in), don't title the widget, and it should work just fine.
All other pop plugins on WP are all changing into commercial poppers where you pay for the views to the plugin maker, not a bad deal, but I think you don't want to pay 30 $ a month
This is a Popunder, because exits have proven to me to be lesser effective. Anyway, it might not be the thing you look for, but it does do something you need.