[Bug]: Adding a query to login/v2/flow results in a wrong redirect for clients

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

https://somenextcloudinstance.com/login/v2/flow/ZD1vrsN3Ed4aTOUyJ68GlZkOSTt4UBTeJKgSCbdNM3O3Qtta2Lvar6MUDjTDG29RfbuEMs1SmAYa8n45eZRJA5dUVoZGGb?user=some.name@somenextcloudinstance.com

Having user as a query in the URL does not do proper redirecting on clients.
Instead of redirecting to the "grant access" screen, it redirects to the Nextcloud home page.
This means we cannot log in to clients.

Steps to reproduce

1. Open a client.
2. Use "import account" or use QR code to log in, to where the email will be auto filled.
3. Observe

Expected behavior

It should lead to "grant access" page so clients can finalize logging in.

Nextcloud Server version

32

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

Start by reproducing the login/v2/flow request with the user query shown in the issue and trace the endpoint's redirect handling. Compare the result with a request without the query; done means client login reaches the grant access page and the import or QR-code flow can finish.