Below linked page lists all environments, technologies, and versions that can be monitored with Dynatrace. This list is continuously growing, so check back often.
The Dynatrace OneAgent SDK enables you to instrument your application manually to extend end-to-end visibility for frameworks and technologies for which there is no code module available yet.
For appliances (I think you are talking about Dell EMC Isilon) you probably want to use the ActiveGate plugin SDK. More info here:
It's very similar to the OneAgent plugin (not to confuse with OneAgent SDK). Plugins are written in python and run on the Environment ActiveGate.
With ActiveGate plugins you can monitor (collect metrics/events) new technologies that cannot run OneAgent. If you need to collect metrics/events for entities where OneAgent is able to be installed and running, then you should use the OneAgent plugin SDK.