Here's a few, from https://www.allsides.com/blog/wikipedia-biased
Six studies, including two from Harvard researchers, have found a left-wing bias at Wikipedia:
A 2024 analysis [1] by researcher David Rozado that used AllSides Media Bias Ratings [2] found Wikipedia associates right-of-center public figures with more negative sentiment than left-wing figures, and tends to associate left-leaning news organizations with more positive sentiment than right-leaning ones.
A Harvard study [3] found Wikipedia articles are more left-wing than Encyclopedia Britannica.
Another paper [4] from the same Harvard researchers found left-wing editors are more active and partisan on the site.
A 2018 analysis [5] found top-cited news outlets on Wikipedia are mainly left-wing.
Another analysis [6] using AllSides Media Bias Ratings found that pages on American politicians cite mostly left-wing news outlets.
American academics found [7] conservative editors are 6 times more likely to be sanctioned in Wikipedia policy enforcement.
There are far more sources out there.
If I show examples of biased pages - the one on Antifa is a good example - this will just devolve into a quibble about this or that sentence.
[1] https://davidrozado.substack.com/p/is-wikipedia-politically-...
[2] https://www.allsides.com/media-bias/ratings
[3] https://www.semanticscholar.org/paper/Do-Experts-or-Collecti...
[4] https://www.hbs.edu/faculty/Publication%20Files/17-028_e7788...
[7] https://thecritic.co.uk/the-left-wing-bias-of-wikipedia/