Comment by atdt

Decompile the apk, and run 'strings' on assets/flutter_assets/kernel_blob.bin.

Poke around and you'll find code for POSTing JSON-encoded credentials to http://35.246.158.51:8070/auth/getUrl. (Grep for the IP to find it.)

So, using the web site name as the seed and the 'client id' as the password, we get:

$ curl -X POST -H "Content-Type: application/json" -d '{"Seed": "3d375032374147a7865753e4bbc92682", "Password": "d7c6bdcfcb184bf587ceee7c7c28e72e"}' http://35.246.158.51:8070/auth/getUrl

The response is an HTTP 200 and: {"AuthURL":"/auth/v2"}

http://35.246.158.51:8070/auth/v2 is I guess the next step.

edit: The /auth/getUrl endpoint responds to any request with the same response, so that may not be the right Seed/Password combination.