I believe that this should be solved client-side in the flutter client by hardcoding the redirect URI to fluxer://auth/sso/callback as the only place the redirect URI is handled server side is as part of the API when the client asks what redirect URI it should provide to the IdP.
The latter part makes sense as this would be individual for each instance, but for the app the redirect never changes, no matter the instance.
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Comment by @frenzeldk
fluxer://auth/sso/callbackas the only place the redirect URI is handled server side is as part of the API when the client asks what redirect URI it should provide to the IdP. The latter part makes sense as this would be individual for each instance, but for the app the redirect never changes, no matter the instance.