@Pradeep Jha (Persistent Systems Inc) Thanks for your patience and your time over offline. I am summarizing our offline discussion and posting the same as Answer for the benefit of other community members.
Issue :
Customer is trying to deploy this Open AI GitHub Sample to B1 function app, and the deployment is getting failed Internal Server error (host runtime is unavailable).
Upon investigating deeper, in this issue #1266 they have clearly mentioned that this Sample cannot be deployed B1 functions app since it will run one core with lesser RAM, and they have suggested to go for B3 plan only.
Also, Bicep template has been updated with B3 as default value for function apps in PR# 646
Hope this help, let me know if you have any further questions on this.
Please accept as "Yes" if the answer is helpful so that it can help others in the community.