The 27-year-old's deal runs until June 2026, with the option of a further year.
Dickie signed for QPR in 2020 and made 129 appearances for them, including 40 this season in all competitions.
The 20-year-old left back, who can also play in midfield, will be released by the Premier League champions at the end of his contract on 30 June.
He was part of the City squad that won the Premier League 2 title this term, finishing 13 points clear of second-placed Liverpool.
Duffy, 31, was released by Fulham at the end of his contract and has signed a three-year deal with the Canaries.
Duffy joined Fulham on a season-long loan from Brighton last summer and on a permanent deal in January.
Millwall have signed Scotland striker Kevin Nisbet from Hibernian for what the Edinburgh club have described as a "significant seven-figure fee".
The 26-year-old spent three years at Hibs and scored 12 goals in 19 Scottish Premiership appearances last season.
Nisbet has been capped 10 times by Scotland and was included in their squad for June's European Championship qualifiers
It racked up a total attendance of 19.8m in the 2022-23 season, the biggest since the 1953-54 season.
All three divisions figured in the top 20 best-attended European leagues, while the play-offs also had record figures.
The Championship total of 10,391,945 fans is the first time for four years the number has broken eight figures.
That made the Championship the fifth-best supported division in Europe, behind the Premier League, Bundesliga, La Liga and Serie A.
I wonder which team was in it four years ago
No doubt the attendances will rise again with Leeds United back in the mix!
Liverpool right-back Calvin Ramsay is to join Championship club Preston North End on a season-long loan.
Ramsay signed from Aberdeen in June 2022 but injuries meant the 19-year-old only made two appearances for Liverpool in the past campaign.
Were we linked with Calvin Ramsey last season?
Apart from the 1st season up...... we weren't really
I'm just WTF-ing my way through life......
we aint been mixing it with the big boys since o,leary was manager no point been in the premier league to be whipping boys every season . we have ended up in the championship due to gross mismanagement on a huge scale , a greedy owner in radrizaani, , a dof in orta who could not spot quality players if they were playing in his back garden, and players who are not fit to wear the shirt .that simply do not have the ability or spirit for a fight , players signed for way over their market value who aint up to the job, wont get this club back among the elite of english football again.