According to data collected by BCN in Japan during March and April, Sony A7III is the best selling entry-level full frame mirrorless camera. The data was collected from numerous retailers from the entire country. As you can see from the graph below, Canon EOS RP had a pretty good start at the beginning of March, but sales started declining shortly after, and have recently fallen below 15%. Sales of Canon EOS R are hovering above 10%, while the Z6 is actually seeing an increase in sales in the latest weeks.
However, the real champion here is the Sony A7III, which crossed 40% mark recently. This means that more A7III bodies are now selling than Canon EOS R, EOS RP, and Nikon Z6 cameras combined. A quick glance at the list of best selling cameras on Amazon confirms that the situation may not be that different in the U.S., although Amazon doesn’t release exact sales numbers.