Steam Client and none steam dedicated server

Hello, so i have been trying for the last few days to connect my steam client game to my dedicated server via direct IP

But as you know you cannot connect to a dedicated server via direct IP if the server has Steam implemented.

so i have been trying to run the server -nosteam and the client with steam.
This does not work, it connects but gets disconnected with error: incompatible_unique_net_id

This is because there are two different OSS OnlineSubSystems

I found this website:

That actually mentions this, but i do not know what exactly they want me to do?
I find the BaseGameMode.h in visual studio but im not sure if they want me to replace everything in the file?

Also the .cpp file i do not find at all inside visual studio?

Can someone please help us out here?
Thanks!