My experience with charging while driving is that it's a trickle charge at best. I only mentioned the propane system as something I had that was thoroughly obnoxious to actually use. Parks won't let you use them at night for a reason and I thoroughly agree with that. I am not a fan of transporting gas cans myself. There are quite a few portable power units like the Jackery and ones from Anker that would provide plenty of juice for charging a drone. I would plug one of those into a charger socket on the vehicle while driving and charge devices from that.
When I charge while driving I use my 110v outlet. When it's parked it puts out 100amps and while driving it's 40amps. More then enough to plug in two charging supplies to recharge my smaller batteries.
I don't have Jackeries as you are paying premium for the name. Mine are GoLabs and they were using the LiPo batteries before Jackery did.
So I have 2 - 300 Wh and 1 - 500Wh, I can use these to power my telescope at night.
For my cameras to power them all night when shooting the Milky Way, I have 4 - 172WH units from GoLabs.
But I can mix and match depending on if I am using 3 cameras or 4 cameras, and whether I need to power a Dew heater strip as well for each camera.
All of these are relatively small, and I have specific places for them to go in my truck.
I do have a 100w Solar Panel, but I have that only for emergency as I have found it charges very slow, and I am never in the same place long enough for it to actually charge what I am using up at night.
Typically I am driving 4 to 8 hours from one location to the next, and that's enough time to plug the batteries into my 110 outlet and get them charged back up for the next night.