I have owned a mirrorless camera since 2015, and used it for lots of stills and video work in rough environments, with plenty of lens changes. I have yet to find any sensor spots that I can't blow off with a Rocket Blower.

I DO practice safe handling and lens changes! Either a lens or body cap is on my camera at all times, unless I'm quickly swapping lenses. I like to do lens changes indoors, in still air, or in a car with the windows up and the engine off. Otherwise, my back is to the wind. As much as is possible, I hold the body FLANGE DOWN when the lens is off. I keep my camera case, rear lens caps, and lens mounts spotless. It DOES help that my most often used lenses are weather-sealed with rubber gaskets.

Contrast that with the days when I used Canons and Nikons (dSLRs). I had to clean those bodies' sensors at least once a year, sometimes twice or three times, using Sensor Swabs and Eclipse. And THOSE were just training cameras that saw maybe 5000 shutter actuations per year, in my training classes.

The dSLR mirror chamber can be a nasty environment. That mirror is mounted on a mechanism that wears. It's lubricated. But over time, bits of metal, lubricant, and the foam dampener the mirror "bounces" off of, just below the focusing screen, come loose. The mirror acts like a giant fan, kicking that crap around until it lands on the sensor during exposure. Both the lube and the foam are sticky. The sensor is statically charged...

How do I know this? Well, when I was in the school portrait industry, we had hundreds of Canon dSLRs in the field. 98% of them used a single 28mm-75mm Tamron zoom lens that never came off during the school year, unless the sensor needed to be cleaned. Those cameras averaged around 400 exposures per camera per day, or 2000 exposures a week for about 15 weeks a year... or 25,000 to 35,000 shutter actuations per year. Even though the lenses seldom came off, the sensors got dirty, and when they needed cleaning, it was either professional cleaning, or Sensor Swabs and Eclipse in the hands of someone properly trained to use them.

Mirrorless cameras eliminate most of the sources of internally-generated sensor dust. But no camera can keep dust out if you stupidly leave the lens or body cap off, or lose your body cap.

Gary Box from OK gave a tip that I have used: they make a small attachment kit for ShopVacs that can be used to suck particles off the sensor. Do NOT touch the sensor! Do NOT get the tip of the attachment too close to the sensor! Do NOT use the small brush attachment in the kit to wipe or brush the sensor (it is not of lens brush quality). Do NOT use the 20HP shop vacs--use one of the lower powered portables! I have used it once. Evidently, I don't get a lot of dust on my sensors. I change lenses in my car if I am doing photography outdoors. Indoors, I cover the camera body once I have removed the lens. The biggest mistake most photographers make is that they remove the lens with the camera body facing up. This permits debris to fall onto the sensor. Hold your camera as if you were going to take a photograph when taking lenses off OR putting lenses on. You will experience a marked decrease in "sensor spots."