I suggest you read the book “2 Live: A Concert Documentary”
by Pimm Jal de la Parra.
According to that book, they played as support band for:
*Revolver, early in 1978 at the Mcgonagle’s, Dublin (they were still called The Hype by then).
*Modern Heirs and Revolver, again at Mcgonagle’s, July 31, 1978 (the band had changed the name to U2).
*The Stranglers, September 9, 1978 at Top Hat Ballroom.
*The Greedy Bastards, a band made up of members of Thin Lizzy and The Sex Pistols, at the Stardust, Dublin, December 1978.
*Patrick Fitzgerald (two shows) in September 1979 at The Project Arts Centre.
*The Dolly Mixtures, December 1, 1979. West Hampstead, Moonlight Club.
*The Dolly Mixtures, December 5, 1979. Covent Garden.
*Secret Affair, December 2, 1979. Earl’s Court.
*The Talking Heads, December 7, 8, 1979, Camden, Electric Ballroom.
*Idiot Dancers, December 11, 1979. Canning Town.
*The Photos, December 12, 1979. Uxbridge.
*Tony Stevens Showband, February 1980. Tullermeny.
*The Talking Heads (Two shows in London and one in Paris), December, 1980.
*Talas, December 8, 1980. Buffalo, NY.
*Barooga, December 13, 1980. Boston, MA.
*The J. Geils Band, March 25,19852. Phoenix, AZ.
*The J. Geils Band, March 29, 30, 1985. San Francisco, CA.
Apart from The Stranglers, The Talking Heart, The Sex Pistols and Thin Lizzy I had never heard of the other bands before.