Firebase Auth in capacitor (native) with SAML

Hi, I want to login with firebase auth and SAML in a native capacitor app.

I use firebase.auth().signInWithRedirect() but it throws
{"code":"auth/operation-not-supported-in-this-environment","message":"This operation is not supported in the environment this application is running on. \"location.protocol\" must be http, https or chrome-extension and web storage must be enabled."}
because I’m native.

The firebase-authentication-plugin doesn’t support SAML.

For cordova there is a solution in the docs:

Unfortunately the cordova-plugin-customurlscheme throws the error:

npm ERR! Invalid tag name "URL_SCHEME=APPID": Tags may not have any characters that encodeURIComponent encodes.

Can I use capacitor deeplinks for this instead?

Can anybody please help with some experience?