We gave up growing any of the Ligularias for that reason. They are as snail prone as Hostas. Try coffee grounds, or copper tape or slug pellets.

We planted one in a wild area near our pond last year, but it was reduced to a leafless skeleton in a few weeks by these destructive little creatures.
My wife dug it up and potted it, and it's been kept overwinter under cover. It's made a beautiful plant which we've planted back in the original place. I've some hostas there too, and amazingly nothing has touched them yet this year. Maybe it's the very cold winter, maybe the fact we have a duck roaming around down there, anyway, it now looks as it might flower successfully without damage.
Unless you've space for a duck, I'd try putting pieces of old thin copper pipe in a square around the plant. You could probably get these for nothing as the offcuts from a plumber's work. It does work to deter snails and slugs as they don't like the electrical static charge which seems to be associated with copper and their slime.

I too have had trouble with snail and slugs on our ligularia and hostas round our pond plus our rhubarb leaves. This year I put down wooly balls, think they are called "Slug Gone", which I got from Wriggly Wrigglers. Problem solved!!!
I have also been using "Slug Inns" round the veggie plot topping them up with Tennants Lager and these have proved a worthwhile buy though hubbie is not too happy about that!!
My daughter reckons coffee grounds are the way to go.