Yes they work. If you have no intention of changing the roof for > 10 years, get one. It probably will be more than enough for a standard sized garage (~ 400 sq ft).

However, I prefer having a passive venting solution. I just removed my solar attic fan after re-roofing with metal shakes. Changing from an asphalt based roofing system to a metal roof made a significant diff (almost 10 degrees centigrade).

I've read a lot of complaints that the solar fans break after one or two years, but have never had one myself. I have a couple of fans at the top of the attic in the louvered vents that have a built in thermostat. I have them set to come on at 100 degrees, I think.
These suck air in thru the soffits, the blow it out up top. Seem to work OK, this is my second year with them.

The solar fan I took off my roof is still working after 5+ years. It is now surplus.

They work okay and might have application value if you are trying to cool a garage but ideal ventilation is passive for the main home.

Attic fans, even solar units, can create negative pressure and exacerbate the air leakage issue for the conditioned space.

Ideal ventilation is passive and move directly under the roof deck.