SQL Server Basic Availability Group: config-only replica?
It is just the configuration data no user data - so probably of limited use
There is more information available here :-
https://docs.microsoft.com/en-US/sql/t-sql/statements/create-availability-group-transact-sql?view=sql-server-ver15
to quote :-
CONFIGURATION_ONLY Specifies that the primary replica synchronously commit availability group configuration metadata to the master database on this replica. The replica will not contain user data. This option:
Can be hosted on any edition of SQL Server, including Express Edition.
Requires the data mirroring endpoint of the CONFIGURATION_ONLY replica to be type WITNESS.
Can not be altered.
Is not valid when CLUSTER_TYPE = WSFC.
For more information, see Configuration only replica.