I've been discussing, in this issue, at Dynatrace OpenTelemetry metrics for JS GitHub repository about the some future support for some of the feature now the deprecated repository covered. And I was instructed to seek for further details here in the community.
Currently Histograms metrics are not supported by Dynatrace according, is there any plans and timeline to start supporting this? This is main reason why I'm using the lib is the conversion it makes to Dynatrace Gauge for the proprietary API.
On this lib there was the possibility to send the metrics to the OneAgent which would send transmit them to the server, avoiding extra costs. Is there the same possibility with the OTLP exporters? Is the OneAgent being enhanced to understand OTLP APIs?
I cannot answer the first question as I understand OpenTelemetry is still a work-in-progress.
As for your second question, I think you can assume that any extra custom metrics that you create with Dynatrace Extensions is going to come at a cost (DDUs). I'm assuming you're are referring to the OneAgent Metrics API?
I believe that there is still a cost associated to custom metric ingestion via that OneAgent Metric API but I don't know for certain.