Hi,
Thanks for trying out the preview image, and thanks for reporting this issue. You can fix this issue on your existing preview image by pointing the kernel to the right conda environment: edit the file /usr/local/share/jupyter/kernels/spark-3-python/kernel.sh
and replace "py37_base" with "py37_default". There are two occurrences you need to replace.
We will publish an updated image soon.
We recommend that you use the preview image going forward.
-Paul