Wikimedia Foundation refuses voluntary union recognition, hires union-busting law firm

A few months ago I cancelled my donations due to them firing a group of workers who stated their intent to unionize.

Where they actually fired? From skimming your linked article it was more of a restructuring, moving them to different positions. The restructuring might be ill advised, though I could not find real information about any connection to the union topic, besides someone from the community claming that, without further information on that connection.