Linhardt was one of my most valuable team members during my route (Black Eagles, Crimson Flower) in the game.
Story-wise, his tale is rather weak. I don’t remember much about him except he liked to take naps.
Which he “apparently” didn’t do as much post-time skip.
In battle his healing and teleporting powers were really useful.
I rarely used him on offense, but he had some powerful magic. But against the stronger beings, they were pretty much useless.