When attempting to run an update on my system today I received an error that the nvidia-dkms-440 package had failed to properly configure. Scanning the log at /var/lib/dkms/nvidia/440.64/build/make.log it appeared that the issue was that the build portion of the configuration was attempting to build the kernel modules with Clang, rather than GCC. For unrelated development reasons I had used the update-alternatives command to specify clang instead of gcc for cc and c++.
Once I realized this I was able to resolve the issue locally by running update-alternatives again to switch back, but I feel I should be able to configure my system defaults without having it negatively impact my video drivers. If the nvidia-dkms-440 package depends on a particular compiler version used to build the kernel, then it should explicitly depend on that compiler and should ensure that it’s used, rather than relying on cc to be pointing to it.