Like a normal adb device, you can dump backtrace of native processes running on a Microdroid-base VM using debuggerd. Use vm_shell tool, and then run debuggerd.
adb -s localhost:8000 start tombstoned adb -s localhost:8000 debuggerd -b {PID}
Note: tombstoned is required for debuggerd, but microdroid doesn't run tombstoned by default, even on debuggable VMs. As shown above, you need to start tombstoned manually, before running debuggerd.