OpenBeken-App Compilation Error: OBK_VARIANT Not Defined in obk_config.h

Hi!
I need some help compiling the OpenBeken-App. I followed the content of the file https://github.com/openshwprojects/OpenBK7231T_App/blob/main/BUILDING.md

1. Cloned the SDK (git clone https://github.com/openshwprojects/OpenBK7231N)
2. Cloned the APP (git clone https://github.com/openshwprojects/OpenBK7231T_App)
3. Moved and renamed the App-Directory to OpenBK7231N/apps/OpenBK7231N_App
4. Tried to compile (sh b.sh)

I got the error:

build ../../../apps/OpenBK7231N_App/src/debug_tuyaMCUsimulator.o
build ../../../apps/OpenBK7231N_App/src/new_cfg.o
build ../../../apps/OpenBK7231N_App/src/new_common.o
In file included from ../../../apps/OpenBK7231N_App/src/new_common.h:20:0,
from ../../../apps/OpenBK7231N_App/src/new_cfg.c:2:
../../../apps/OpenBK7231N_App/src/obk_config.h:302:18: error: operator '==' has no left operand
#if (OBK_VARIANT == OBK_VARIANT_BERRY || OBK_VARIANT == OBK_VARIANT_TUYAMCU || OBK_VARIANT == OBK_VARIANT_POWERMETERING || OBK_VARIANT == OBK_VARIANT_IRREMOTEESP)

As far as I can see, OBK_VARIANT is not defined.

Do I have to use a specific commit of the SDK and the App?

Best regards,
Matthias

AI: Could you please specify which commit hashes or branches of the SDK and the App repositories you used when cloning them?
SDK 2a31abb043f469dd603defef9c94966973d4805a
APP c23984d7e39ad63cf226e34637bafa502325c5ea
AI: Did you make any modifications to the source code or configuration files (such as obk_config.h) before compiling, or did you follow any additional setup steps not mentioned above?
No modifications made, no additional steps made

It's a rather outdated guide.
Remove everything, clone OpenBK7231T_App, cd to it and use "make OpenBK7231N".

Not successful on my Win10 PC. The error is:

Create symlink for OpenBK7231N into sdk folder
ln -s "/c/Users/user/Desktop/OpenBK7231T_App/" "sdk/OpenBK7231N/apps/OpenBK7231N"
ln: failed to create symbolic link 'sdk/OpenBK7231N/apps/OpenBK7231N': Too many levels of symbolic links

On my Debian PC it compiled successfully.

Thanks a lot!