Fresh install on a pi400

have a pi400
got a freedombox on sdcard
working after startup
got to see a wifi possibility (FreedomBoxwlan0) on another pi400

but no info on which login to use


There isn’t a pre-set login for FreedomBox. You will need to connect to the web interface of the FreedomBox, and create the initial user account there. You may be able to access the web interface at http://freedombox.local on your local network, or else will need to find out the IP address of the FreedomBox. This page has more details: FreedomBox/Manual/QuickStart - Debian Wiki