Dev.to app asks me to type in my github username and password into the github login page opened in their app. Is there no better way to do OAuth on Android apps?

Hello. (Android) dev here contemplating about the future of my profession.

I am looking for a specialization or a field in my profession where i can be free of dependencies from GAFAM (The big five)
Basically software development is me only using dependencies and stuff they and 3rdparty people have created and then it works or it doesnt. Or if you dont keep it up2date it wont work because deprecation and breaking changes. I was web developer before and changed to android because of all the libs and frameworks one needed to wield for proper development. And now android has mostly become the same. Vanilla android is easy, but u start using google apis or 3rdparty services u quickly realize how far u get away from your actual usecase. Usermanagement, oauth, 2fa, userdatamanagement, crossplattform, offline, syncing etc.

I am pretty sure the topic came up before (dev fatigue, dependency fatigue) and most of you know what i mean but i might be the recent casualty here.

Hey i want to make a chat application for production workload with more than 100000 simultaneous connection and more than 1000000 daily active user which will scale 100 times in coming 1 to 2 years for Android. I have oauth based user authentication. This chat should be able to authenticate and verify authtoken generated using the oauth. What should i use? Xmpp, mqtt or something else. Can anyone who has worked on chat application help me.