I agree, and I never thought about this, I have used dry powder in earnest to put out a fire in our Dethleffs camper. Horrible stuff, and the aftermath from the powder has to be seen to be believed. Breathing in, or eye contact I reckon would not be nice, with possible after effects?
Repeating myself, and a simple task, as our camper has only one access door, which already has a secondary door security measure, making an addition simpler.
Look at at your door/s, ask your self, what can I do to beef up entry from undesirable’s, be it diy or off the shelf. Fit it, as it can buy you time to get your head together to take positive measures to keep you safe.
If you think back to films set in the middle ages and/or properties from that era which showed people securing the doors internally and a common method was dropping a big wooden plank across the door resting on two "U" brackets. Modern version could be shoot-bolts. The biggest problem is finding a position strong enough on the doot to mount on.
Now I can't recall where I saw this next thing, and I don't know what it is called so can't search for it, but maybe the description will ring a bell .....?
There is an aftermarket product that can be used with Hartal type motorhome habitation doors. You take this product, which I think has a C-shape and simply slide it over the internal moving lock part - either top one or bottom one, or even get a pair or them? When they are in position, it prevents the bolt, that moves up or down when you pull the handle, from moving. Doesn't matter if the door is locked, unlocked or the has been forced, it physically cannot be opened. I guess a bit like a deadlock in effect.
Very simple, and I bet some folk on the forum could work out how to make one pretty easily?
Something everyone muct keep in mind .... the more secure you make your motorhome, the harder - and longer - it might take you to exit in an emergency, or something to get in to help you if you could not help yourself? All a matter of getting the balance right.
FWIW, I have a a house-style alarm in my own motorhome. I have PIRs internally and magnetic sensors on the doors (including cab doors) and lockers and a siren. And like a house alarm, I can set it to be "Away", so all active including the PIRs, or "Home", where the mag sensors are active and the PIRs are off. So if I set to "Home", if anyone opens the doot middle of the night, after a few seconds the Siren will go off. I also have a remote keyfob to enable/disable the alarm plus an "SOS" button for instant activation.
Maybe having something like that could be a good option? Mine also interfaces with the Alexa in the van and I have the alarm activasting a message on the Alexa speaker telling the incomer to get out and they are being recorded from the internal Blink camera.

These kind of alarms are not expensive at all. Little search for something like "wireless shed alarm" say might be a goof starting point?