By the way, the link was garbled. It should be [ANN][RFC] strict-mutable-base - strict variants of mutable data types from base
deepseq is an anti-pattern, an extremely expensive and blunt hammer, generally costing O(n) time to do what should take O(1) time. It is as much as a footgun as unexpected laziness.
I have explained the problem of and solution to space leaks due to unexpected laziness in more detail in these articles:
My library strict-wrapper paired with @TeofilC’s th-deepstrict should be all that is required to design algebraic data types without hidden laziness and therefore without space leaks.
Beyond algebraic data types, the suggestion to add versions of IORef, MVar etc. that don’t hide laziness is completely in line with that strategy, but that does not require deepseq.