I have Ligularia ’The Rocket’ in a similar position and it does very well, growing to 6 feet with multiple tall spikes of yellow flowers. There are other and different Ligularias which would grow well there, too, like L. Dentata 'Marie Britt Crawford' which I also have.

Many very much

Ferns would be great.

ferns would be my first choice, lots of different shapes and shades of green too. then there are hosta's also.

Yes, I agree about ferns and hostas, too. These would all look great together tiered down to the front. Keep a lookout for slugs. This sort of corner is slug heaven!