I don't know of a place that is leash free.
Keeping that in mind, for my money there is no better place to camp on the river than River Lodge - second to the last place up-river on the Cal side, about 2 miles south of the dam.
The show of boats passing the island, the closed in cliffs, the cool beaches (there are three), lagoon for overnight mooring - it adds up. They have electric or non-electric campsites. All have water.
Negative - beeing far upriver makes shopping something to plan in advance.