There are lots of small OSS businesses that are contractors to the big companies you mention. My go-to example is Igalia, who work on web browser and other core

There are lots of small OSS businesses that are contractors to the big companies you mention. My go-to example is Igalia, who work on web browser and other core OSS tech, but there lots of others, some mentioned on the FOSSjobs wiki. https://www.igalia.com/ https://www.igalia.com/ https://github.com/fossjobs/fossjobs/wiki/resources https://github.com/fossjobs/fossjobs/wiki/resources