My setup: Macbook Pro late 2013 -> Thunderbolt Cable -> Sonnet Adapter -> Express Card -> Multiface

I've just upgraded by MBP from 10.14 to 11.5.2 Big Sur. Installation of driver 4.21 succeeded, but the kernel extension is not loaded during boot.

If I manually load the extension (/Library/Extensions/HDSPMADI.kext) everything works fine.

Any idea what might cause this issue?