Android/Fire beta 109.15.250:
On my Fire TV edition Insignia 24" set, the What's Next card still appears at the beginning of each episode. When it is visible, I cannot skip or fast-forward. New behavior in this beta: after I dismiss the card, I still cannot skip or fast-forward at all. This is worse, as I used to be able to skip just not fast-forward. There is one improvement, however. The What's Next card does not appear each time I try to skip or fast-forward.
On my Fire TV edition Insignia 50" set, the What's Next card does not appear at the beginning of each episode. Skip and fast-forward work fine. I'm still not sure how to use the What's Next feature, but at least it does not interfere with my navigation.