Open edX is a huge stack and it requires at least 4GB of RAM memory in order to work as expected. Could you please double-check that you have enough free space in your Ubuntu VM.
On the other hand, the link you shared with us describes the steps to install the official Open edX which is not the Bitnami Open edX stack.
This is documentation you have to check in order to use the Bitnami Open edX Stack:
I hope this information is useful for you. If you have any other questions, please do not hesitate to let us know.