Yes! I have great things to say about buckwheat.
It sprouts quickly, has big enough leaves to shade the ground so that any weeds that can sprout do poorly. If you have 6 weeks before frost, you have enough time to plant it. Cut it before it sets seed. Honey bees and other pollinators like it, so let it flower for them if you can.
If you have a long season, you cut it, let it sit on the ground for a week or two, and plant another round. I tried to till it in, but the stems wrapped around the tiller tines, so that didn't work well.
One year, I did three courses in an area I wasn't planting that season. VERY few weeds the next season.
It dies with frost, and does not come back. It does not fix nitrogen. Its gift to you is shading out the weeds so they can't grow, and adding plant material to the soil.
