Word of mouth probably and the ones that know how to use a computer. Good maps are important in the outback so if they know about Open Street Map or osmAnd then I'm sure they will hear about Mapillary.
The biggest limiting factor is uploading. Internet quotas are too small (unlimited does not really exist for mobile/cell or at caravan parks/motels) as well as upload speed.
The place I stayed for 2 nights only gave 1.5GB to use and was only a bit better than what I have at home. I used the final hours to upload a little bit before leaving but the rest of the 35,000 images I uploaded at home which took almost 4 days with no other services running - day and night except for when I was out and capturing more.
This is with the low resolution set in Mapillary and still using version 3.27. Using normal resolution would take weeks and high resolution would take months.
Grey nomads would fill up memory and have little in the way of actually uploading it even if cost is not the factor.
Resolution and quality settings in the app is something that needs to be clarified unless it has been in newer versions I have not tried yet. A JPEG 60 quality 1080 x 720 image is better than no image at all because uploading takes too long that people give up.