2016, in a 5–0 win at Crewe Alexandra. On 14 January 2016, Armstrong's loan was extended until the end of the season. He finished the season scoring 20 goals in his 40 Coventry appearances. In April, he was listed in the PFA Team of the Year for League One. Barnsley (loan) Despite making two appearances for Newcastle at the start of the 2016–17 season, on 30 August, Armstrong joined fellow Championship side Barnsley on an initial six-month loan deal, having signed a new four-year deal at St James' Park before his departure, after Newcastle manager Rafael Benítez expressed his desire for Armstrong to gain more experience at Championship level. He made his debut for the Tykes on 10 September as a substitute in place of Ryan Kent during a 2–1 victory at Preston North End, scoring the winning goal with a left-footed curling effort after outpacing and losing his marker with a backheel. In January 2017, it was announced that Armstrong had extended his loan spell at the club until the end of the 2016–17 season. Bolton Wanderers (loan) On 17 July 2017, Armstrong joined Championship side Bolton Wanderers until the following January. He made his debut for the club on 6 August, coming on as a late substitute for Stephen Darby in Bolton's 3–2 home defeat to Leeds United before making his first start in the EFL Cup at Crewe Alexandra, scoring in a 2–1 win. Armstrong was recalled from his loan spell on 4 January 2018, having made 23 appearances in all competitions. Blackburn Rovers On 9 January 2018, Armstrong joined EFL League One side Blackburn Rovers on loan until the end of the season. He helped Blackburn secure promotion to the EFL Championship at the first time of asking. Armstrong signed for Blackburn Rovers permanently on 6 August 2018 on a four-year contract for an undisclosed fee believed to be in the region of £1.75 million. Throughout the 2020–21 season, he scored three hat-tricks, coming against Wycombe Wanderers, Huddersfield Town and Birmingham City. Armstrong scored 64 League and Cup goal in his 160 appearances for Rovers, including 29 goals in his final season with them. Southampton On 10 August 2021, Armstrong joined Premier League side Southampton on a four-year-deal for an undisclosed fee, reported to be in the region of £15 million. He scored on his debut for the club, a 3–1 defeat away to Everton on