Make a background (pure black is fine) 1080x720 pixels, and save it. Use Gimp, Pinta, or any other image editor to do this.
Then load the image again, and put the first line of the lyrics in with the "text" function. I know Gimp has it; other image editors probably would as well. Save as "frame1.png" or any other naming convention you want to use.
Make another frame for the second line of the song. Continue until you have frames all the way down the song.
Note: There are no real shortcuts for this process, and it is hard and time-consuming.
Then use OpenShot, or ffDiaporama, to put them together with the song. I don't know any video editors (except Windows ones) well enough to give you tutorial-level instructions on that part, unfortunately.