Lakka on Ubuntu 19.10 on RPI 4

So, there’s official support for Raspberry Pi 4 from both, Lakka and Ubuntu 19.10. I’d like to install Lakka as an app on the Ubuntu, which is to be the main OS on the RPI 4.

How do I get around to it? There’s the SD card way, but the card slot is already going to be occupied with Ubuntu 19.10. How to install Lakka then?

Lakka is an OS that runs RetroArch (this is the app). As you already have another OS (Ubuntu), you simply install RetroArch on that.

There is a PPA for Ubuntu (link), and you can also compile it yourself.