It is surprising that Prelude.Linear exports the non-linear version of projection fst :: (a,b) -> a.
This tripped me up (with non-inspiring errors about multiplicity) when writing evalState:

• Add evalState (to Control.Functor.Linear) #404

I was naturally expecting that fst :: Consumable b => (a,b) -> a would be by default in scope if a fst is in scope. After all, we want linear programs when we import Prelude.Linear!
So, I suggest either to not export fst (and alike) or export them from Data.Tuple.Linear.