I think the suggestion of having a build that people can use to find problem sites is a great idea. Unfortunately it’s quite intrusive as there’s no way to install it alongside the default browser.
I can’t think of a cleaner way than replacing all of these packages:
sailfish-browser
sailfish-browser-settings
embedlite-components-qt5
qtmozembed-qt5
xulrunner-qt5
If anyone is up for giving it a go I could put together some instructions. But I absolutely wouldn’t recommend doing this on a daily device I’m afraid.