Can the AppCenter do it just like how Ubuntu Software does?
It seems like AppCenter lacks lots of apps.
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Sign up to join this communityFirefox is already available in AppCenter.
AppCenter doesn't support the installation of Snap packages at this time
i think if you want you can, since loki is built on ubuntu 16.04 first install snapd
sudo apt install snapd
then install snap applications normally.
For example to install a simple app just run sudo snap install hello
to see the installed app use snap list
to run an installed app use snap run hello
if you need to know more how to manage and install snap apps refer this link https://goo.gl/aFfwvM