Jonathan Kuminga's frustrations with the Golden State Warriors have been apparent essentially all year. Steve Kerr yanked Kuminga's playing time throughout his tenure as a Warrior since getting drafted, and that's why both sides are ready to move on.
The Phoenix Suns and Sacramento Kings have each submitted offers for a sign-and-trade for Kuminga, but nothing has materialized yet. Kuminga could opt into his qualifying offer and enter unrestricted free agency next offseason, but the Warriors would prefer to find a solution this offseason.

Sam Amick of The Athletic appeared on 95.7 The Game to discuss Kuminga's situation, going into why the Warriors are willing to let Kuminga go to another team.
"Steve Kerr is somebody who has obviously, at times, been frustrated by the limitations in Jonathan Kuminga’s game, and it's pretty evident that the Warriors are willing to move on."
So, why not remove the qualifying offer and let him walk? The Warriors need something of value back to build around their current roster, and the best way to do that is in a sign-and-trade.
"The thing that they are trying to salvage here is that they really need that salary slot. You know, there's only so many ways for them to meaningfully add to this roster and try to continue the Steph [Curry]-Draymond [Green], now Jimmy Butler era, and if Jonathan takes the qualifying offer, then you're pretty limited when the February trade deadline comes around...."

What are the Warriors Looking for in Return for Kuminga?
All reports have indicated that the Golden State Warriors would like a first-round pick and at least one young player in return for Jonathan Kuminga in a sign-and-trade. It's been hard to find a team willing to give that up so far.
The Sacramento Kings have reportedly offered Devin Carter, Dario Saric, and two second-round picks, before upping the draft capital to include a lottery-protected first-round pick. Both of those offers were declined, as the Warriors really want an unprotected pick.
Meanwhile, the Phoenix Suns have reportedly offered Nick Richards, Royce O'Neale, and four second-round picks, according to ESPN's Marc J. Spears. Because there wasn't a first-round pick attached, the Warriors weren't interested at all.
The Warriors may need to adjust their expectations, or there's a chance Kuminga could walk for free next year, and that would be a worst-case scenario.