I was able to get most cores to work by manually adding the arm64 core builds from GitHub - christianhaitian/retroarch-cores to the libretrocores folder in Retroarch. This post was very helpful:
However, you can also just straight up install RetroPie on this system, which require less tinkering to get functional cores installed and also provide emulationstation, which is a nicer interface:
cd
git clone --depth=1 https://github.com/RetroPie/RetroPie-Setup.git
cd RetroPie-Setup
chmod +x retropie_setup.sh
sudo ./retropie_setup.sh
Basic Install >> Quick Install
You can also switch the menu driver in Retroarch from rgui to xmb, which will switch to the higher resolution blue interface that’s more familiar from desktop installations (although I personally think the pixelated version has its charms).