Shaders not working on Mac M1 after 1.21.9 update

After updating to Minecraft 1.21.9 on a Mac M1 (2021), shaders no longer load correctly.
I was previously using OptiFine 1.21.8 HD U J7 pre14 with BSL Shaders, and everything worked perfectly.
I have tried multiple free shader packs similar to Fabulous, including BSL Shaders and Sildur’s Vibrant Lite, but none of them work now.
Shader zip files are correctly placed in the shaderpacks folder, and I am using Performance graphics instead of Fabulous.
This issue seems specific to Mac M1, as shaders worked fine before the update.

Platform: Mac
Version: 1.21.9
Category: Bug Report