Thanks for posting your question in the Microsoft Q&A forum.
Read-Only Endpoint: This endpoint can be configured by users to point either to a read replica or the primary server. However, it can only target one server at a time. Load balancing between multiple servers isn't supported. You can adjust the target server for this endpoint anytime, whether before or after promotion.
** Please don't forget to close up the thread here by upvoting and accept it as an answer if it is helpful **