They sell a Zwift virtual gear shifting. It should be working on the Rouvy app, but it is extremely unstable. When you start by connecting it to Zwift and then go to Rouvy, it somehow magically works. Why? Because they don't want you to use Rouvy. Even Rouvy themselves can't get through to them. I initially thought of using Zwift, because some friends do, but I have no respect for these methods.
BS company.