Hey man, we’re living parallel lives. I literally just did this yesterday. The command you’re looking for is gdebi. Try gdebi (name of the package’s file, uncompressed to a .deb) if you downloaded the .Deb from the website. tic80 will now be a usable command. To uninstall the tic80 command / program you can use apt uninstall tic80. It worked with and without sudo.