There are at least seven bands/artists named Jack.
1. The most popular Jack at the moment is a Dutch rapper based in Rotterdam, The Netherlands, who released the albums 'Plan A' and 'Plan A Deluxe' in 2019 and 'Traplove' in 2020.
2. Jack is a Grindcore / Crust band from Hungary. Originally started off as a Hardcore Punk band, but then they got faster.
http://jackgrindpunk.bandcamp.com/
3. Formed in Cardiff, Wales in 1992, the band Jack is based around the songwriting partnership of Anthony Reynolds and guitarist Matthew Scott Read more on Last.fm