OH. You dont have Mint installed. You have Manjaro with the KDE desktop and not Cinnamon. Now it makes sense why the sudo apt command doesnt work, lol. You dont have apt. Apt is the package manager for debian based distros which Mint is.

I dont have much experience with Manjaro I would have to refer you to their forums and search for Pinebook pro on there.
https://forum.manjaro.org/

Either that or to install something else such as Armbian which is Debian based with the Cinnamon desktop.
https://www.armbian.com/pinebook-pro/

Then whatever software you install from now on make sure it is specifically for ARM and not amd/intel. You want to look for things that say ARM or ARM64.

I wanted to get my hands on one of those Pinebook Pro's when they first came out and I still would love to have one to play with, lol. They look like a lot of fun.