Open Terminal
Go to the folder containing the .deb file
Run `sudo apt install ./package-name.deb`
Enter your password if prompted
Wait for the installation to finish
If needed, fix...
Identify the drive and mount point:
`lsblk -f`
`df -h`
Unmount the drive:
`sudo umount /dev/sdXN`
Create a mount point if needed:
`sudo mkdir -p /mnt/external`
Mount the drive:
`sudo mount /dev/sdXN...
