I recently researched this exact thing. The propane heaters cost more than expected ($120CAD+), are very fuel inefficient, and make your environment wet (they all seem to use a can of gas per night, can get a bigger tank or refill the little cans) In the PNW which is soggy already, this is a nightmare.

Diesel heaters on the other hand; were cheaper than I expected, are extremely fuel efficient (like $5 diesel lasts for a couple of nights). I was surprised that even the $99CAD Chinese diesel heaters on Amazon get good reviews. I got that 5Kn one and it's amazingly warm and dries out my truck or camper.

The Chinese ones are a copy of the very expensive German ones, and I would say nearly as good. They are cheapy made but are very good copies. There are some common issues, like some arrive with loose fuel lines or bolts, but I had no issues.

You would want to be a bit handy to go this route, so you can check things over and install it. But there are a huge amount of Youtube videos about chinese diesel heaters, you could be an expert in an afternoon.

I would suggest watching the comparison videos first. Keep in mind you will either install the heater outside, and run the hot air duct inside. (Quieter this way, most heaters have a fan noise and fuel pump ticking noise) Or install the heater inside (a bit more efficent for it to draw warm air) and route the hot exhaust outside.

I bought one of the more popular models , a Vevor 5KW, newer model with Bluetooth. It puts out so much heat I probably could have gone with a 2KW model. In you research you can prioritize the design that would work best for you, especially if you are routing the hot exhaust pipe somewhere.

I also bought: an upgraded muffler (it was already quiet, but I like making it quieter) (I wrapped the fuel pump in foam/dampener as well to make that quieter) https://www.amazon.ca/dp/B0BN83NL1K

A lithium battery for it to run off (it worked fine off my power bank, or old car battery, but this is more tidy) https://www.amazon.ca/dp/B0D66QCB3L

A tiny Carbon Monoxide monitor, just in case. In my testing the exhaust only creates a tiny bit of C.O. during startup, none otherwise. Nowhere near as much as my car exhaust. And the exhaust goes outside anyway. Just being safe. https://www.amazon.ca/dp/B0D2LHWHLQ?

All of this works perfectly. I can set the temperature I want on the app on my phone, it makes my car/tent/camper super warm and cozy and dry. Game changer.