I believe that you can only use them with a commlink, yes.
Cyberdecks? Non sequitur. They don't allow you to access the matrix. You have to use a Cyberdeck in conjunction with a commlink or cyberjack.
Cyberjack? Unnecessary. It already allows you to use VR.
Commlink? That's what it's for. A sim module doesn't have a Device Rating because it's a modification for your commlink, it's not a separate device.
RCC? It's not a commlink, and in the case of riggers they already have a sim module thanks to their Control Rig. If someone else is using a RCC, I do believe the RAW answer is "it can do what a commlink can do, plus these other things..." but it's technically not a commlink. I know in 5e it was the case that anything "for commlinks" did not also work on RCCs.