Why are my cumulative metrics not ingested?

[alexander_dt]

Dynatrace currently does not support cumulative aggregation. Make sure to configure a delta temporality.

[SirineMaslah]

how to modify the delta temporality ?
My attempt to map the environment variable to delta was unsuccessful.
(export OTEL_EXPORTR_OTLP_METRICS_TEMPORALITY_PREFERENCE=delta)