SOOC: Straight Out Of Camera
Spelled out, that acronym has nothing to do with processing. It simply indicates an image exactly as it comes out of the camera. That covers every image you export from your camera. What you do with an SOOC image is a different story. The term is usually applied to JPEGs used "as is", but it actually gives no measure of what processing has already been done in-camera.
So, yes Virginia, SOOC does exist.

In the finest UHH tradition......!

I'm 74 and I won't concede that any new toy is my last until I get old. Still, if I were to make my "final camera upgrade" it would be the R5. It's the best of all the Canons you list and who doesn't want the best as their last? The Sony? I know nothing about it but it would have to be some camera to beat the R5.

Of course you can, but the OP's question inferred that no processing had taken place, as opposed to pp. Actually, SOOC is deceptive. Any image you transfer out of your camera is SOOC. The difference is that theJPEG has already received some level of processing while the RAW image has not, but almost certainly will.

Curious as to why you feel that the most expensive adapter is necessary. Even with the least expensive adapter your lenses will have full functionality. A separate adapter for each lens? When I bought my first mirrorless, an R, I had a bunch of EF lenses. Most of the time I left the adapter on the camera. It has a cover just like the body cover on a DSLR so dust getting in was not an issue.
I had a 5DIV. Now I have an R5. The 5DIV was a good camera but it doesn't come close to the R5.

Einstein had a good sense of humor. That was just his slightly humorous way of saying "Don't try to oversimplify".

Back in '88 when I was first learning to skydive one of the first things I and every other student learned was how the equipment worked. At one point I mentioned to the instructor that "this stuff is idiot-proof". He replied: Yeah, but the problem is that as soon as you make something idiot-proof someone else invents a better idiot.

Neutral is just a point on a sliding scale and in itself is a choice. Exactly what neutral is though is not determined by the photographer but by the camera. So yes, the photographer does not have total control of JPEGs. To me though the term "post processing" does not differentiate between who or what does the processing, only whether or not processing occured.
Interesting conversation, but it is bedtime. See ya later.

You're right, they don't know who is going to use what batteries. That is why Canon, and no doubt the other manufacturers, will license, probably for a per battery fee, the firmware necessary for their batteries to work with the cameras. Provided the batteries meet Canon's standards and the battery manufacturer is willing to pay the fee. Counterfeiters and cheapos won't pay the fee or even meet the standards. Those are the batteries that are going to have issues. Buy a Wasabi, a Watson, or any of a dozen other good quality 3rd party batteries and they will work. Certification and licensing are common. Companies pay close attention to that because in many cases it cuts down on warranty payouts.

I consider your definition of pre and post to be as valid as anyone's, including my own. However, if you believe that adjusting the presets to neutral or center means that the camera does no processing I would have to disagree. That would mean that the JPEG would come out looking the same as the RAW image. I have never specifically checked, but I don't believe that would be the case. I believe that even set to neutral the presets are still going to produce changes to the image captured by the sensor. Plus, I think that it is a safe bet that there are JPEG parameters that the user can't change when shooting JPEG.

Gotta love it! The OP has a battery issue and before you can blink it becomes a conspiracy by that evil camera company to separate customers from their last dollar, with the assumption of course that the company cares not at all about customer satisfaction yet expects those customers to stay loyal and keep buying their products. Next thing you know we will be hearing about camera company employees going around kicking customers dogs and scattering their garbage.

Depends on what you consider "post" to mean. For some people it would appear that it means processing done after the image is exported from the camera. For me post means any processing done after the image is captured by the sensor. The sensor captures RAW data which the camera almost instantly converts to a JPEG based on the camera settings. That, to me, is post processing since the image is first captured then converted. Whether you shoot in JPEG or RAW the sensor collects the same RAW data. The camera is just quicker to process that RAW image then you are. Despite how anyone defines post processing SOOC really has nothing to do with processing. It just defines an image that was used exactly as it came out of the camera. Rather common with JPEGs but RAW images aren't usually too impressive SOOC. Hmmm....Maybe that explains some of my images. I was shooting RAW without knowing it! Yeah, that explains it!
On that note, I have to say that the RAW images from my R5 are much closer to being "right" then with my previous cameras. No idea why. I wonder if anyone else has noticed that.

Less is more.
Rent or buy a good quality bridge camera with a decent optical zoom and spare battery. (You can always sell the camera when you get back). Don't make your photos your only memory of the trip because you spent all your time taking pictures, lugging equipment, and worrying about what to use.
Case in point: During a trip to Oahu I took a doors-off helicopter tour of the island. Took a lot of pictures. Two days later I took the same tour again. Only took a few pictures. Spent my time enjoying the view. The pictures are nice. The memories are better.

If you consider pp to be any changes made to an image after the sensor collects that image then everybody uses pp. JPEGs are processed in camera based on settings put in by the manufacturer, many of which you can change, BTW. RAW images require processing in your computer. Either way, there is processing involved.
If you shoot JPEG there are a number of camera parameters you can change to get a better image "SOOC". If you shoot RAW it just takes time and practice to get the best out of the image.

Really? T3i, 70D, 6D, 5DIV, R, R5. With each of those Canons I used both Canon and 3rd party batteries, Watson and Power2000, and I always kept the firmware for each camera up to date. No compatability issues. The only battery issue I have ever had was a Canon LP-E6 that came with my new 6D. Right out of the box new and it wouldn't take a charge. B&H replaced it no questions asked. My R5 uses 3rd party batteries with no problem.