Cannot set up lock screen – Error message "A screen lock is already set," but none exists / Sperrbildschirm kann nicht eingerichtet werden – Fehlermeldung "bereits aktiviert", obwohl keiner existiert

[piero]

Hello @stem, Welcome to the /e/ users forum.

@piero

things you must take care about

Warning: Before proceeding with the installation, log out of any accounts you may have set on the stock ROM. Also, remove any screen locks that have been set on the device.

to solve your problem, you will have to restore FairphoneOS, then log-in / log-out to your Gogol account, and finally reinstall /e/OS.