OMEN OF AMELIORATION FARM

Is there a way to target farm them?

Probably ritual. Wiki says it is level 46, so I don't think you can get it from act 2.

I think with the lantern it might of been possible to farm a bunch of omens from drops, don't think that that is available currently. There might be some other ways. The wiki mentions a connection to wildwood, maybe that is a way, but probably a low chance with multiple layers of RNG.

"The Viridian Wildwood can sometimes contain an Omen Cairn that drops a random Omen when interacted with."