Can't build keras model after Tensorflow update from 2.2 to 2.3

As @ebgoldst suggested, installing TF 2.2 is the fix here.
Since the TF 2.2 binary distributed by pip is linked against libcudart10.1, you may also want to install that as well:
pip3 install tensorflow==2.2.0 && sudo apt -y install libcudart10.1

New workaround:

pip3 install -U protobuf