Originally posted by Munin:

We know it is annoying. The downloads are caused by a Steam setting called 'Shader Pre-Caching' and this has nothing to do with Iron Gate or Valheim in general.

Please refrain from creating new threads on the topic matter!

These small updates are pre-compiled GPU Shader downloads. Shaders help Vulkan and OpenGL games to load faster and improve framerate stability during gameplay.

If you wish to disable this option, just disable Shader Pre-Caching here:
Steam > Settings > Shader Pre-Caching