Bury, Dagenham & Redbridge did not return after participating last year, meanwhile Ipswich Town did not return after 4 years in the competition, Barnsley, Brighton & Hove Albion, Cardiff City, Middlesbrough, Watford, and Wigan Athletic did not return after 5 seasons in the competition.
Notts County returned after competing in the inaugural competition, Doncaster Rovers, Leeds United, Peterborough United and Plymouth Argyle returned after a 2 year absence competing for the first time since 2015-2016, Fulham and Reading after last year's absence.
Newport County and Oxford United participated in the competition for the very first time this year.
A qualifying round was required to finalise the 32 teams that would enter the Group Stage.
Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply.