SHOW REPLICA STATUS, and the terminology that changed

8.0.22 deprecated the old replication vocabulary in favour of source and replica, and every script and runbook contains the old words.

-- deprecated, still works, prints a warning
SHOW SLAVE STATUSG
CHANGE MASTER TO ...
START SLAVE;

-- 8.0.22+
SHOW REPLICA STATUSG
CHANGE REPLICATION SOURCE TO ...
START REPLICA;

-- and the column names changed too:
--   Seconds_Behind_Master → Seconds_Behind_Source
--   Slave_IO_Running      → Replica_IO_Running

The column renames are what break monitoring rather than the statements, because a check parsing Slave_IO_Running from the output finds nothing and reports healthy — a failure that is silent in exactly the direction you do not want. Both spellings work for several versions, which is generous and is also why nobody migrates until the old one is removed. Grepping the monitoring configuration for the old column names is a ten-minute job worth doing at the upgrade.