Compatability with LTspice?

I fully agree with @bordodynov , this is only additional information for reference.

Device Compatibility
The major device not compatible from LTspice is A-device, which unfortunately is commonly used in LT and AD devices subckt. Two reasons that A-device is not implemented in Qspice according to Mike Engelhardt

Depends on how A-device is used in LTspice model, it may or may not be translate into Qspice. But no matter how it done, there is no way for full compatibility from A-device to Ã-device.

If A-device is not involved, you should generally able to work between simulators with netlist. Schematic file is always unique to the simulators GUI, but netlist is universal (sometime you may still need few modification). This is a common method that people use it to compare Qspice with different spice simulators.