Summary
In 2020, the Pistons essentially traded Drummond away as a salary dump, despite him only being 26 years old and a two-time All-Star. While part of that was just due to his big contract making it harder to trade him, the reality was that Drummond never developed enough on either end to really be a franchise player.

Despite putting up solid numbers for the Cavs to start the '20-'21 season, the Cavs were unable to find a trade partner for Drummond and ended up buying him out, leading to Drummond signing with the Lakers, and eventually signing just a minimum contract with Philadelphia in free agency in 2021.

Drummond is not the lob threat that he was when he was younger, and those that compared him to Dwight Howard early in his career were always overstating Drummond's athleticism. He also never became the defensive presence that many had hoped, as his instincts on that end aren't good enough to make him a great rim protector.

Drummond has always been a high-volume rebounder, although there has been some debate about the value of his rebounding. There were many seasons in which his teams rebounded better when Drummond was off the court. The thinking there is that it doesn't matter who gets the rebound, as long as your team does, so certain players like Robin Lopez and Steven Adams who box out their man and let their teammates grab rebounds are actually more valuable than guys like Drummond, who mostly grab uncontested rebounds.

However, Drummond has also been a really good offensive rebounder, which is almost always a positive as it's hard to "steal" offensive rebounds from teammates. He's a legitimate big body that can bully smaller players down low, and has nice touch around the rim. While he isn't the best rim protector, his size alone can be helpful at times.

Drummond actually has some off-the-dribble ability, although he can sometimes get a little too carried away with that. While he's not exactly Nikola Jokic, he does have some passing ability from the high-post. Drummond also has the ability to make a dribble or two as the roll man and make a play toward the rim, as opposed to some centers who can't do anything except catch and go up with the ball.

Drummond had a decent season backing up Joel Embiid in Philadelphia, then even started for the Nets after being traded. I think it's possible that he played his way out of a minimum contract, but I would be surprised if he got much more than the minimum.
 
Cap Considerations
Drummond will be an unrestricted free agent with a $1.8 million cap hold and Non-Bird Rights. This means that the highest starting salary the Nets could offer him using the Non-Bird Exception is $3.4 million. This should be enough to retain Drummond, since he settled for the minimum of $2.4 million in 2021. Alternatively, the Nets could use their Taxpayer Mid-Level Exception to re-sign Drummond if he demands more than $3.4 million.

Other teams will have multiple ways to sign Drummond as even teams without cap space could possibly use any of the Non-Taxpayer MLE, Taxpayer MLE, or possibly even the Room MLE or Bi-Annual Exception to sign him. Since he signed a minimum contract in 2021, teams will hope to get him at the minimum in 2022 too.