I do not doubt the second law in general, just if it rigorously applied to the entire universe. Here's why I ask this
2nd law - restricted to isolated systems: "The second law may be formulated by the observation that the entropy of isolated systems left to spontaneous evolution cannot decrease" https://en.wikipedia.org/wiki/Second_law_of_thermodynamics
Fluctuation theorem - restricted to finite systems: "...for a finite non-equilibrium system in a finite time, the FT gives a precise mathematical expression for the probability that entropy will flow in a direction opposite to that dictated by the second law of thermodynamics"
"...the FT does not state that the second law of thermodynamics is wrong or invalid. The second law of thermodynamics is a statement about macroscopic systems. The FT is more general. It can be applied to both microscopic and macroscopic systems. When applied to macroscopic systems, the FT is equivalent to the Second Law of Thermodynamics" https://en.wikipedia.org/wiki/Fluctuation_theorem
Irreversible processes - only in finite time: "In reality, however, truly reversible processes never happen (or will take an infinitely long time to happen)" https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Thermodynamics/The_Four_Laws_of_Thermodynamics/Second_Law_of_Thermodynamics
Doesn't the whole universe violate all 3 of these conditions? It is not isolated, not finite spatially, and infinite in the future. And even for the observable universe, isn't it infinite in the future? This at least violates #3, and I would think #2 as it will be spatially infinite in infinite time.
Can you at least answer how the observable universe isn't infinite in the future to satisfy #2 (i.e. it will keep expanding and thus be infinite spatially) and #3?