Well, a 300W solar panel will provide you with ~ 2.5 kWh of power in a day with 8 hours of sunlight. The average overlander seems to pack 3 panels to unfurl and get power from. Let's say they get around 6 kWh of power from this setup in a day.

The R1T get's around 2.2 miles per kWh in combined usage. So you'd get maybe 13 miles of usable range from a day of sitting around, assuming flat roads and not going uphill all the time (I couldn't tell you what off-roading usage would look like). Alternatively, assuming 1 kW per hour to run climate control, you could get 6 hours of AC a day.

That doesn't seem like much, but the thing is that this is free power that can be split between cooling/heating the car or driving, and you can still carry a generator with gas cans to potentially charge the car. Likewise, it isn't as though you would be going out somewhere to the point of getting to 0% SOC. You'd probably want to leave half of the battery full for the trip back.

Is it ideal? No. Can solar power give this car infinite range? No. However, in the grand scheme of things, an ICE car cannot charge off solar but an EV could. I think solar panels could be fine as a sort of medium-term backup system or 'range-extender' for trips where you would be fine being stationary for awhile. However, you would need good access to sunlight and need to be realistic about how much power you could actually draw from the panels.