Summarized changelogs:

• 2021.4:
  • Support Vulkan 1.3.
  • Support targeting SPIR-V 1.6, which is the default for Vulkan 1.3.
• 2021.1:
  • Disable --target-env=opengl_compat with an explicit error message. It has been deprecated for a long time.

Other releases include only dependencies updates and build fixes. Full changelogs here.

Tested Vulkan video renderer in mpv (it uses libplacebo for Vulkan calls, which in its turn uses shaderc for translating GLSL shaders to SPIR-V).