the nextclouddb folder is full, the database and log arguments are present, and there is also a custom.cnf file and the setting is done.
I have completed the installation of linuxserver / mariabd seamlessly, but my network-> AppData-> nextclouddb folder and custom.cnf file is absolutely empty.
It looks from your screenshots that you are running this on an RPI? It looks like you are pulling the x86 image and not the armhf image. This goes for mariadb also. You should be using the lsioarmhf/mariadb and lsioarmhf/nextcloud for repository.
The second thing is you mention that the appdata folder is on a network share. This is not something we recommend, and you will get issues.
It looks from your screenshots that you are running this on an RPI? It looks like you are pulling the x86 image and not the armhf image. This goes for mariadb also. You should be using the lsioarmhf/mariadb and lsioarmhf/nextcloud for repository.