The fog appears to be calculated wrongly, thus it doesn't appear circular. It appears it's instead based on the back of the scene, like the fog was with fast graphics around the time of 1.14. In other words, the fog is closest to the camera at the center of the scene than on the edges. This bug is shows up with the blindness and the darkness effects.

Environment:

• Minecraft 1.19 with Quilt Loader 0.17.0, Sodium 0.4.2+build.16 and Iris 1.2.5
• Adoptium Java 17.0.1 on Linux amd64 on mesa drivers.
• MakeUp UltraFast version 8.6

The non-circular fog, blindness and darkness issue is resolved in version 8.6b (legacy branch), and in the same version in CurseForge.

Changes to the develop and master branches of Github will be included later.