UiPath Assistant for macOS will allow you to run attended cross-platform automation. RPA developers will use UiPath Studio in Windows to create cross-platform projects and publish them to Orchestrator.
When designing a process for macOS in Studio, the testing is done using Remote Debugging and connecting to the specific macOS machine.
Regarding activity packages available for cross-platform, currently, our teams are working on adding new capabilities and in the next releases, you will be able to use more of them.
More details can be found here: UiPath Assistant for macOS