I just had and resolved this problem.
The “Sign in with AWS” button load from federated component.
The solution is to override the slot in amplify-sign-in with an empty div.
Eg :
<amplify-authenticator
*ngIf="authState !== 'signedin'">
<amplify-sign-in slot="sign-in" usernameAlias="phone_number" hideSignUp>
<div slot="federated-buttons"></div>
</amplify-sign-in>
</amplify-authenticator>
<div *ngIf="authState === 'signedin' && user" class="App">
<amplify-sign-out></amplify-sign-out>
<div>Hello, {{user.username}}</div>
<!-- This is where you application template code goes -->
</div>
CLICK HERE to find out more related problems solutions.