Just finished Vikings Valhalla. I enjoyed it, and it was a sharp contrast to the early seasons of Vikings that revolved around Ragnar. An amazing performance by Travis made those seasons of Vikings work, and you can't expect most actors to carry a series like that. Not to mention, you're going to lose a lot of of your audience when you lose the character and/or the actor, no matter how good the rest of the series is.
Valhalla was pretty balanced, focusing more on stories and a variety of characters - not so much on an individual character. I don't know a lot of the actual history of that period. So, I can't evaluate it on that basis. But again, I enjoyed it.