You can increase source angle or source radius to increase the penumbra size (make it softer), which reduces visible aliasing.
For local lights, you can reduce r.Shadow.Virtual.ResolutionLodBiasLocal, e.g. to -1 to increase resolution.
For directional lights, there is a similar r.Shadow.Virtual.ResolutionLodBiasDirectional.
As mentioned above, local lights with large cone angles or large attenuation radii can also hit resolution limits.
In the viewport viewmodes menu, you can use the “Virtual Shadow Map → Clipmap/Mip Level” viewmode to see what resolution level is used for the shadows.