Bear in mind that the USSR moves before England does (OOB) and before America and England (Alpha 2) thus it can be used for the “Can Opener” maneuver as well. (Pop a blocking destroyer so the war fleets can sink the Italian/German navy and invade Hamburg/Frankfurt Germany, Berlin Germany, Rome Italy, whatever.)
If for no other reason, moving the Russian submarine to the combined Anglo-American fleet in the Atlantic might be worth it.
And, to belabor the point, it is another defending ship if your Anglo-American fleet is ever attacked, and one that neither England nor America has to purchase.
Note, these are the same arguments for using the Russian Submarine in previous versions of the game. It’s always been semi-useless, but it has also always had a use in the rare situation it was needed. Sometimes it was America who had to make a hole for the Russian due to the turn order, but it was the same basic situation. Another unit that the Axis have to account for if you use it properly. Sure, if you sit the submarine off the Cape of Good Hope (S. Africa) the Axis can virtually ignore it. If it’s near Panama, the Axis can ignore it. But why not use it as another unit with the Anglo-American flotilla? It does not cost anything, it cannot be used to defend Russia in any meaningful way and if you do not use it thusly, you are essentially giving the Germans (and maybe the Japanese if you move it to the Pacific/Indian Oceans) a 6 IPC bid. (8 classic, but you dont start with a submarine in classic)