What is the OVNR joke?

This joke is a clever play on words that references a famous song lyric while also relating to the game of Scrabble. Midge Ure is a musician known for his work with the band Ultravox, and one of their most famous songs is “Vienna.” A well-known line from this song is “This means nothing to me,” sung during the chorus.
In Scrabble, players create words using individual letter tiles, and the joke is that the person playing with Midge Ure has only four letters left: O, V, N, and R. These letters, when arranged, do not easily form a recognizable English word. The player humorously remarks that these letters “mean nothing to me,” echoing the famous lyric from “Vienna.” The humor arises from the coincidence of having these particular letters while playing with the singer who made the line famous, and the double meaning of the phrase – both in the context of the song and in the literal sense of the Scrabble game.