I want to enable ads in certain websites, but not globally, create an exception list of some sort for the ad blocker. Is that possible? Without checking and unchecking "block ads" in preferences, of course.
This has been requested several times, but unfortunately it's not currently possible. https://gitlab.gnome.org/GNOME/epiphany/issues/268 has been reported to add this functionality.
May 2019 edit: this will be possible in Epiphany 3.34 using the security popover that appears when you click the address bar lock icon; various website permissions will be available to change there.