Lightning damage... I was told that if I am lucky it only killed the component in the picture, which can be replaced. Problem is, I can't find it anywhere, so if anybody knows, I would be grateful.
You could try checking the continuity of that signal transformer's windings with a meter if you think some of them are burnt out.
Like you I've not been able to find anywhere on the internet that sells that chip. I think you'll have to look for an equivalent device. The AG1801DS looks to be identical. Maybe you can find somewhere that sells that.