Things I’ve tried:
- Using Film > Pixel Filter > Type > Gaussian, width 4px made it a little better, but the whole picture became blurry;
- Denoising, nothing;
- Lots of render samples (1000), it only removed the noise but not the jagged edges;
- Increasing the values for the Subdivision modifier doesn’t smooth the edges.
I don’t use any render settings, I just hit F12 and it rendered my other projects just fine. I don’t use the compositor thing too, but I don’t know how to mess with it.