We call it webapps.
It’s can be found once you want to access your router administration via HTTP or HTTPS (e.g. http://192.168.1.1)
By default, you can find there Foris and LuCI. If I remember correctly, @miska has added for now integration for these packages: Transmission, TVheadend, Nextcloud.
How you can add webapp yourself for applications, which you want can be found here from this commit.
Basically, you need to add the configuration file to /usr/share/turris-webapps. One of those files, which are there can be used as an example. Copy it and edit it to correspond with app, which you’d like.
You’d need to add the icon to /www/webapps-icons
And that’s all.
Right now, I’d like to add there netdata as well, but any requests are welcome, however, I’d need to ask you to create a separate thread for it.