I have imported my external conda environment through Administration>Code Envs>New Python Env>Named External Conda Env. I have validated that Dataiku is able to import this env correctly by going to MY-ENV>Packages>Fetch Packages List, which displays the conda and pip packages installed.
I created a Python Recipe and opened a notebook. However the message "Could not find a kernel matching Python (env MY-ENV). Please select a kernel:" appeared, with the kernel options being only Python 2 or Python 3.