For those looking for a premier wilderness paddling experience on a beautiful river that isn't exceptionally difficult, the upper North Fork Trinity offers a spectacular hike-in/paddle-out run that can be done in a long day trip or--better--as an overnighter. This run is particularly well-suited for packrafts. This has been run twice (to my knowledge), once in early June and once in mid-late May both during low snow years. Both trips yielded lower than ideal flows with lots of butt dragging. With California's current pattern of weak winters, aim for early May but it's possible in a high snow year that it could run well into late June. At low flows, it was all class 2 rock dodging, boulder garden style rapids with the exception of Hobo Drop. At more enjoyable flows some of the rapids may turn into class 3.
Start by hiking on the North Fork trail headed upriver from the Hobo Gulch Campground. After about 5 miles, you'll reach Rattlesnake Creek at its confluence with the North Fork Trinity. This creek puts a lot of water into the North Fork. Depending upon snowmelt, the North Fork may be low upstream of Rattlesnake Creek. You can put in the North Fork here if that's the case and you'll have a 4.8-mile paddle back to Hobo Gulch Campground. But, if the North Fork has adequate flows above Rattlesnake Creek, you can continue hiking upriver four more miles, passing the historic Jorstad Cabin, to put in at the confluence with the next major tributary: Grizzly Creek. This yields an 8.7-mile run that makes an ideal overnighter.
Rattlesnake and Grizzly Creek are both large enough to be navigable at decent flows but have not been attempted. Rattlesnake Creek has a gorge/waterfall section and I didn't scout above that. Grizzly Creek has a few navigable miles.
Packrafter Justin Baker's video gives an excellent overview of this run:
Upper North Fork Trinity River Packrafting, Grizzly Creek to Hobo Gulch Campground, May 2021.