The
access the App management page of Nextcloud, click on “+ Apps” link in the
Settings Menu.
You will see the “App page” of Nextcloud (refer to the next diagram).
In that page, you will find currently installed App, whether in enabled or disabled state, any update available for your apps …etc.
You can browse through and search for additional
app that may be useful or applicable to your need.
Note: As there are a variety of apps and most are created by third parties, iWV does not warrant the functionality of such apps and there is no support or very limited support for such apps.
You can browse https://apps.nextcloud.com/ to find out
more on each app and its associated documentation (if exist).
It
is a good practice to keep your apps updated.
If an app is shown as, 
it
means that particular app is not tested against the current version of Nextcloud
that you are using.