Hi @Robert94
1. Go to https://make.powerapps.com/
2. Choose the right environment
3. Select Apps> Choose your portal > Three dots > Settings > Authentication Settings
4. It will open up the identity providers
5. Choose Azure AD> Three dots > Select "Remove as default"
Note: If you don't see remove as default, try disabling the Azure AD and then you can re-enable it later

I have a blog about this please click here
Please feel free to hit the follow button on my blog 😛
Optional:
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In Design Studio
1. Pres sync configuration and preview the website. And press "Ctrl+F5"
Hope it helps.
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