Recovery Area is not enabled.

SQL> alter database flashback on;
alter database flashback on
*
ERROR at line 1:
ORA-38706: Cannot turn on FLASHBACK DATABASE logging.
ORA-38709: Recovery Area is not enabled.

setting DB_RECOVERY_FILE_DEST to directory - leading to broken parameters and database did not start:

SQL> alter database mount;
alter database mount
*
ERROR at line 1:
ORA-01078: failure in processing system parameters
ORA-00600: internal error code, arguments: [ksfd_odmchkpathattr], [ORA-00001:
unique constraint (.) violated], [], [], [], [], [], [], [], [], [], []
ORA-17503: ksfdopn:13 Failed to open file
/opt/oracle/oradata/fast_recovery_area
ORA-17500: ODM err:Operation not permitted

kubectl -n oracle patch singleinstancedatabase sidb-sample --type merge -p '{"spec":{"flashBack": true}}'
singleinstancedatabase.database.oracle.com/sidb-sample patched (no change)

kubectl -n oracle get singleinstancedatabase sidb-sample -o "jsonpath=[{.status.archiveLog}, {.status.flashBack}, {.status.forceLog}]"
[true, false, true]root@master:~/deployments/oracle#