I found this note on apple site:
Note
In macOS 11 and later, kmutil replaces kextload, kextunload, and other earlier tools for loading and managing kexts. The older tools still work, but their implementations now call kmutil.
panz
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I solved this by myself.
First of all as of macOS 11 every third party kext should be located in /Library/Extensions in order to be loaded by the system.
And every time you rebuild it and try to load it with kextutil you will be prompted with a SystemPreferences app request you must approve and after that you will be allowed to load the kext only after rebooting the system. So as far i understand you should repeat this process every time for every rebuild.