No, the star would heat the Dyson sphere, and it would be observable in infrared. Plus you would need several Dyson spheres for each 'naked' star to explain dar

No, the star would heat the Dyson sphere, and it would be observable in infrared. Plus you would need several Dyson spheres for each 'naked' star to explain dark matter and they need to be build at a constant ratio of start to galaxies for all galaxies we observe.