Does adding matrix-off: newtab.about-scheme false to your rules help?

This means nothing to uBlock Origin, this is a uMatrix rule.

@brson By default uBlock Origin does not mess with about:-based pages. So disable the setting in Firefox (I've never seen any ads on my side in the New Tab page). You may want to use the logger to see if there are network requests related to these ad tiles -- don't forget to check the behind-the-scene network requests.

By default uBlock Origin is disabled on browser-specific pages (about:, chrome://, etc.) in order to ensure it does not interfere with the functioning of the browser or other extensions, I don't intend to change this.

You could set browser.newtabpage.enhanced to false. This wouldn't be likely to break other add-ons, since it's the same pref that the built-in gear checkbox flips. Dunno if users would consider that "interfering with the functioning of the browser" or consistently disabling ads.

I did post this a while ago: https://github.com/gorhill/uBlock/wiki/Tips-and-tricks-waterfall#techcrunch-firefox-will-soon-get-sponsored-suggested-tiles-based-on-your-browsing-history.

Can't tell if this works though (for some reasons no ads here).

Thanks for the link @gorhill.