Hey!
As @Arkiras said above, the sparkling might be an effect of light reflections down on single-pixel levels.
In OP’s post the issue was with directional lights, which is new for me. I have however encountered the issue with other light sources. In those cases, the solution is to increase the size of the light sources. On a spotlight or point light, you can increase the “Source Radius” and/or “Soft Source Radius”, on a Rect Light you can simply make the lightbox larger. This will slightly alter the look of your lighting, but you might find a good balance with some low values. I went with 40 here, and it solved the issue completely in this particular scene.
To summarize what others already have written and I’ve tested myself, here are some options for making the sparkling less extreme, although these options might not get rid of it entirely:
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Slightly increases the roughness of the material that sparkles.
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Decrease Bloom intensity in the post-process volume.
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Change Bloom mode to Standard if you currently use Convolution
To test if your changes remove the sparkling without having to render each time: Go to “Show → Advanced → Temporal AA”. Unchecking that box lets you see the sparkling as it would look while rendering.