I tried to overwrite the next āBenutzername oder E-Mailā (Username or email) with āBenutzernameā (username) because our users donāt have a email adress added but sometimes try to login with their email adress.
The modification was done by editing the files de_DE.js and de_DE.json. The modificated files are located in /themes/custom/core/l10n. de_DE is set as standard. The same goes for the theme custom.
I did the modifications directly in the core/l10n (/var/www/nextcloud/core/l10n/), and works fine!
The cache was troll me. But after I cleared the cache the translation appear in the login page.
strangely, there seem to be some phrases that donāt change for me to. (in my case the āUser disabledā phrase in the en_GB language).
I have also forced the default language in the config.php. @camilobg, how did you reset the cache?
I have forced reload in my browser and restarted the apache server which should also clear the APCu cache. I have also restarted the redis caching.