https://wccftech.com/ac-odyssey-pc-patch-1-03-avx/

Ubisoft has rolled out AC Odyssey PC Patch 1.03 which addresses the AVX CPU issues alongside improvements to performance and stability.

The update fixes an issue which prevents users from starting up the game when using a CPU without support for the AVX instruction set, also known as Sandy Bridge New Extensions. In addition, Ubisoft writes that the update offers various “quality-of-life” and usability improvement features.