2. The Lakers and Cavaliers work out a James sign-and-trade
This option is more complicated than the prior but is far more realistic to happen. LeBron could decline his player option, then the Lakers could sign and trade LeBron to the Cavs.
The Cavaliers don't have a lot of cap space to work with, so this would take some creativity on their end. But if LeBron decides to make it clear he is going to move on from LA, they could be on the search for a sign-and-trade partner. Cleveland has a handful of young talent and veterans to offer the Lakers, keeping LA relatively competitive without James.
The Lakers surely would try to get Donovan Mitchell in the trade, but that doesn't mean the Cavaliers would have to do that. If a package based around Darius Garland is the best offer they receive, they would have to consider it given the circumstances. Also, LeBron could make it clear the only sign-and-trade he would agree to would be from Cleveland, putting LA in a position to be flexible with their trade return.