Securing third party keyboard traffic

We are facing a situation where users are complaining about the default Samsung Keyboard that comes with Galaxy devices as the corporate device. We are looking into providing other options such as Gboard and Swiftkey but the problem is we are unable to fully secure traffic going to these third party services.  For Gboard there are some options onthe MDM as amanaged app while Swiftkey does not have many options. Main reason we stick  with Samsung is the Knox service plugin which helps secure the device more including keyboard however it only applies to samsung keyboard. With each other keyboard we introduce we have to rely on the key value pairs that come with the app to select options we can lock down as needed. Not all the app developers are enterprise focused so its hard to get any feature requests thoguh. Only other thing I can think of is blocking traffic at a network level to ensure nothing goes through but then we would need to know the addresses that are used. Has anyone faced this situation?