Azure Load Testing (Preview) has a limit of 250 threads per Engine Instance. Each test can only run up to 45 Engines, so the theoretical maximum number of concurrent sessions that can be run is 11,250.
I need to simulate 120k concurrent users. Is there a suitable workaround to do this with ALT?
I think it's better to contact Azure Support for the details.
In the mean time be informed that you don't need 3rd-party providers to run a JMeter test without any limits, given you have a subscription you can
which is pretty much what Azure Load Testing is doing under the hood