The 33-year-old has not fought since knocking out Bogdan Dinu, 35, in November 2018.
'Big Baby' was denied a license to box just days before he was due to fight Anthony Joshua and was banned for two years after failing multiple drug tests.
But Miller's promoter Dmitry Salita revealed the boxing bad boy is busy hard at work in the gym as he bids to get his career back on track after a two-year long layoff.
Salita told The Sun: "He is getting back in shape with a mind set to be the best in the division.
"He wants to be an American heavyweight champion of the world from Brooklyn, New York. We haven’t had that in a long time.
"Jarrell always did kickboxing training even for his boxing fights.
"It helps him get in shape and maybe one of the reasons why he is so athletic and flexible in the ring for a heavyweight."
Back in 2019, Miller tested positive for GW501516, causing the New York State Athletic Commission to deny him a license to box.
Joshua was forced to search for a new opponent and ended up fighting Andy Ruiz Jr after Miller tested positive for two other banned substances and was removed from the June 2019 bout.
But if that wasn't bad enough, the New York native failed yet ANOTHER pre-fight drug test, which caused him to be dumped from a comeback fight against Jerry Forrest in July 2020.
However, Salita is confident his client can turn his reputation into something positive.
When asked if Miller should expect to receive a harsh reception from the fans for his doping violations, he replied: "That is going to happen. I believe Jarrell learned his lessons and knows that he has several years to make a mark in the division.
"Positive, responsible action inside and outside the ring is what is most important and something that fans will look at, can’t blame anyone for that."
Miller, 33, has not won a fight since beating Dinu, 35, via fourth-round knockout in 2019.
But the former WBO-NABO heavyweight champion wants to challenge WBC heavyweight champion Tyson Fury as he prepares to embark on the comeback trail.
Salita said: "That fight maybe the biggest heavyweight promotion in a long time. It can be very exciting.
"One step at a time but that would be tremendous."News Now - Sport News