No, I didn’t come up with a suitable solution. I feel having to show a loading icon or hiding elements leads to poor UX and probably page bounce. I ended up ditching dynamic pages and setting the sort and filter on the dataset objects via the editor. Efficiency dividend lost, but at least it’s a better user experience.
It could be that setting the sort and filter in $w.onReady isn’t the right place, but since nobody from Wix responded, I can only guess…