X_OTLP_PROTOCOL_UNSUPPORTED
Means
the OTLP protocol requested is not OTLP/HTTP JSON
Typical cause
OTEL_EXPORTER_OTLP_PROTOCOL asking for grpc or http/protobuf. This exporter speaks one wire format and no dependency ships a second — refused at construction rather than negotiated down
Fix
unset OTEL_EXPORTER_OTLP_PROTOCOL (or set it to http/json) and point OTEL_EXPORTER_OTLP_ENDPOINT at the collector's HTTP receiver, e.g. http://otel-collector:4318