An Azure service that provides an event-driven serverless compute platform.
@Volodymyr Krasulia Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.
I have tested the above shared cmdlet in our environment and without passing the --plan I am able to set the httpsOnly property of function app without any issues.
It is hard to determine why you are landing up in conflict error when trying to update/set/change the settings of the function App. I would suggest you check the activity logs of the function app/resource group to know more why the conflict error occurs.
In general, conflict error occurs when the function app is in busy state, or the earlier operation is still in progress and not able to perform this operation.
Refer to this documentation for more information about common deployment errors.
Feel free to reach back to me if you have any further questions on this.