If the frequency response of a system is time-independent, is this system LTI?
LTI means Linear Time-Invariant systems. The system has to satisfy two conditions.
(1) Linear and (2) Time-Invariant.
(1) Linear means, if the response of the system due to load Px and Py is Rx and Ry respectively, then for the load (Px+Py), the response of the system will be (Rx+Ry).
(2) Time-Invariant means, the parameters of the system does not vary with time.

If the frequency response of the system is Time-Independent, then it suggests that the parameters of the systems are not changing over time, i.e., the system is time-invariant.

But it does not say anything about nonlinearity. Hence, in a nutshell, if the frequency response of a system is time-independent, this system is NOT an LTI?