I don't think there is a solution, as TFrazier said the genie is out of the bottle, now there's no going back.
You could try something like the NFL but that doesn't solve the problem and in some cases would make it worse.
A player signs with an NFL team and has a 4 year contract where he stays for 4 years before he can go. Maybe college gives a 4 year scholarship but there is no transfer portal. Does a team like Nebraska now lose out on good players because they are afraid they are stuck for 4 years with no way out. But then maybe a player is afraid of not playing if he goes to a big time school because he's not good enough.
College has a 20 million cap where they can give money to players, kind of like the NFL salary cap. But in college the big money problem is the NIL going to a player from some business, which has no connection to the 20 million cap.
In the NFL the team has a salary cap, but players can still go out and sign contracts with businesses worth millions of dollars, which has nothing to do with the team cap. College is the same way, we have the 20 million, but at the same time big time players can get millions just for going to a school.
But there is one big difference between the NFL and college that gets in the way of college being like the NFL. The NFL has a draft where a player doesn't really have a choice where he goes, at least for the first contract, while college has recruitment where kids can go anywhere they want if they have an offer.
