You can check when the game was last updated, so if it was updated recently you'd know that it's on the latest version. I think a good way to check this is compare the last update on mobile (mind you steam and itch.io should update a lot sooner than any other platform, Android being the 2nd fastest to be updated and then iOS dead last as always LOL) and see if they dates link up and that's probably a good way to check.
I can't remember if steam indicates when the game was updated, so if there is a way to check when the last time the steam version was updated then that's actually more accurate way of comparing the update times to see if either are on the same version or not.