MySQL 8.4 LTS was released on 10 Apr 2024. When running gh-ost on version 8.4.3, I ran into issues where we had assumed certain commands such as SHOW MASTER STATUS / SHOW SLAVE STATUS / START SLAVE / STOP SLAVE to work.

Version 8.4 of MySQL officially removed support for the old commands.

Reference: https://dev.mysql.com/doc/refman/8.4/en/mysql-nutshell.html (see Replication Syntax)