has been the website/blog Wings Over Scotland: https://wingsoverscotland.com/about/
Set up in 2011 by occasionally abrasive ex-video games designer and journalist Stuart Campbell (his Twitter feed can be controversial at times), its main focus is Scottish independence, but its methodology is forensically (and often colourfully) picking apart media misreporting and myths from a leftist viewpoint.
The very well-visited blog (250,000 readers a month is not unusual) is crowdfunded, and its annual appeals regularly raise prodigious amounts of money from individual donations very quickly (Wikipedia estimates it's raised over £540,000 since 2013).
Vuelio rated it second only to Order, Order in its annual blog rankings.
In the run-up to the Scottish referendum, Campbell published "The Wee Blue Book", a compendium of myths and their debunking that was widely distributed online and in hard copy and is credited by many with changing minds on the subject of independence. Its approach has been copied by a number of other campaigns, from the group Scotland In Europe to the more controversial Yes California. WOS also funds independent opinion polling from time to time.
WOS's success depends very largely on the skills and personality of Campbell (who does occasionally host paid contributions from other writers), so its use as a model for other groups may be limited, but it's an under-covered success story among the "alt-left" media.