UltraStar Deluxe is a free open source karaoke game for your PC. It records the voice of the players and gives points if they hit the notes. Unlike the commercial alternatives, UltraStar Deluxe allows users to add their own songs.

For the Flatpak release the songs need to be placed into ~/.var/app/eu.usdx.UltraStarDeluxe/.ultrastardx/songs/.