Hello there,
I used your tuto for installing MariaDB and Nextcloud on my Zima OS (thanks for your work !) but when I try to create the user for Nextcloud, I always have the same error :
Did you follow the video on YouTube?
Yes that’s exactly what I did 
You can’t change the DB login details from the environment variables once it’s started, only through the DB directly.
Could you be more specific on how to do that please ?
Any answer please ? 
It looks like you changed the DB credentials. Uninstall and reinstall by following the video.