I tried the auto-populate feature, and it doesn’t work perfectly with Elementor. The first populate still shows all the results, and only the second one (i.e., reload the page or start searching) creates the include rule.
Anyway, on the category pages, I set the include rules on Elementor and the Ajax plugin, which works great.
On the ‘Browse All’ page (where I had the sorting by random problem), I also set it from both Elementor and the Ajax plugin to order the results randomly, and it works.
If you confirm that I can continue with these settings and there are not likely to be compatibility issues, everything now works perfectly…