On April 19, 2019, Carter made his NXT UK debut in a dark match, which he lost to Kassius Ohno. He was utilized as a jobber until November 16, where he ended his losing streak. He teamed with Ashton Smith to defeat The Outliers (Dorian Mak and Riddick Moss). He returned to the brand on January 17, 2020, where he teamed with Smith to defeat Pretty Deadly (Lewis Howley and Sam Stoker). On March 7, he participated in a battle royal to determine the next challenger for the NXT UK Championship, but failed to win the match.
On the June 2, 2022 episode of NXT UK, Carter and Smith won the NXT UK Tag Team Championship by defeating previous champions Moustache Mountain (Trent Seven and Tyler Bate) and Die Familie (Teoman and Rohan Raja) in a triple threat match. On the June 23 episode of NXT UK, Carter and Smith were set to defend their titles against NXT 2.0's Josh Briggs and Brooks Jensen, but Smith suffered a knee injury and had to vacate them.
On the September 13, 2022 edition of NXT 2.0, vignettes began airing promoting Carter's debut for the brand, under the name Oro Mensah. In his debut match, Mensah defeated Grayson Waller to qualify for the NXT North American Championship ladder match at Halloween Havoc. At the event on October 22, Wes Lee would win the match. On the November 4 episode of NXT Level Up, Mensah defeated Xyon Quinn. On the March 28, 2023 episode of NXT, Mensah competed in a 20-man battle royal to claim a spot in the fatal-five-way NXT North American Championship match at Stand and Deliver, eliminating Quinn, but ultimately being eliminated by Jinder Mahal. On April 25, at Spring Breakin', Mensah lost against the debuting Oba Femi. On May 28 at Battleground, Mensah turned heel and joined Jakara Jackson and Lash Legend in helping Noam Dar retain his NXT Heritage Cup against Dragon Lee. On the June 13 episode of NXT, Mensah competed in Dar's place due to injury, losing his Heritage Cup to Nathan Frazer. Afterwards, Mensah began a feud with a debuting Ethan Page, who revealed himself as Mensah and Dar's mysterious attacker, effectively turning him and the rest of The Meta-Four into faces. During week two of NXT The Great American Bash on August 6, Mensah challenged Page for his NXT Championship, but lost.