This is what we found on Wikipedia regarding the Boxxer:

Boxxer, stylised as BOXXER, is a British professional boxing promotional company.

Founded by Ben Shalom, Boxxer began as Ultimate Boxxer, organising eight-man professional boxing elimination tournaments starting in April 2018 and preceding to host a total of six tournaments under the original name. In August 2020, Ultimate Boxxer rebranded to Boxxer, and announced its first signee; the winner of the Ultimate Boxxer 3 tournament, Derrick Osaze. The following month, and under the new branding, Boxxer announced its seventh tournament, "Boxxer Series 7", would take place in November 2020 with a new four-man elimination format.

In June 2021, it was announced that Boxxer had signed a four-year deal with Sky Sports. In September, Boxxer revealed their roster of fighters, including Hughie Fury, Savannah Marshall and Caroline Dubois, as well as co-promotional deals with Claressa Shields and Chris Eubank Jr. A co-promotional deal was also made with Bob Arum's Top Rank in regards to the world title fight between Josh Taylor and Jack Catterall. Boxxer's first event on Sky Sports was a co-promotion with Wasserman Boxing, featuring Eubank Jr. on 2 October 2021.

The most notable, high profile event associated with Boxxer was between domestic rivals Amir Khan Vs Kell Brook on 19 February 2022.