Installing a package from external storage (help needed)
So, I have a device running stripped down Ubuntu and I wanna get tic80 on it, I have a copy on a flash drive but idk how to install it. The machine is pretty much CLI only
That depends on how you have mounted the device, as this is usually not done automatically. As I understand, your system doesn't have a desktop environment.
So the you need to search e.g. the output of sudo dmesg after plugging in the USB stick, there should appear s.th. like /dev/sdb1 or alike. Then you can mount the partition e.g. to /mnt directory
sudo mount /dev/sdb1 /mnt
You anyway can check the output of mount (without arguments) if and where the device was mounted successfully.
So you need to build from source, as I don't see a prebuild version for RISC-V on their Github-page. As your system probably is supposed to be slim, you can try cross building from source on another computer. But if you are interested in doing that, please ask in a separate post, as I've never done that.