Loading a new test plan as part of the test plan execution itself is not supported. For this kind of use case it is recommended to create a custom operator panel. You can check out an example here: GitHub - opentap/operator-panel: Operator UI Example Project.
You could also have a test plan with sub-sequences for each type of device, maybe using test plan reference and then skip parts of the plan conditionally, depending on the loaded device.
I’m also looking for a solution to this, can you elaborate a bit how the Operator UI could be a solution?
The Test Plan Reference step would solve the issue if the Reference path property could be resolved at runtime ( a previous step to set it). As I know it works only if the path is set an steps loaded before the plan is running, could this be changed?