Install applications in Ubuntu core
To get some apps not snapped yet on my Ubuntu Core arm i used the classic snap:
sudo snap install classic --devmode --edge
then
sudo classic
then apt-get is available
No, Ubuntu Core is completely snap-based: apt is not available. Ubuntu Core mostly targets headless or kiosk-type devices, and as such doesn't ship with a window manager etc. Kiosk software typically uses Mir. You probably don't want it for a normal desktop environment; you can install snaps on the classic desktop release.