TRACY_ON_DEMAND does not work with fibers
I think I have found a bug.
When using and TRACY_ON_DEMAND at the same time my capture is failing with an "Instrumentation Error" (below). But the error disappear if I remove TRACY_ON_DEMAND.
I have made a test app to reproduce the issue: tracy_fiber_test.zip. You can compare "OnDemand" and "NotOnDemand" build configuration.

It's not so much of a bug, rather a lack of implementation. All that has to be added for this to work is tracking the per-thread fiber state in some data structure, which can be then pushed to the server on connect. The hard thing is to figure out all the edge cases.
I've run into this issue personally.
Is this something an unfamiliar set of hands can help with?