Prius 2017 electric package noise

If it hasn't been done, your 2017 is due for coolant change and transmission fluid service. (Just drain and fill.) Any car mechanic should be able to handle those for you. You might, also, want to get the brake fluid and pads checked.

 

If it's the high-frequency squeal you're hearing, it may be a side effect of how the inverter works. In that case, it's normal.

Instead of creating a pure sinusoidal output of varying frequencies to drive the AC electric motors, the inverter works by generating Pulse Width Modulated outputs. The switching is done at a high frequency, which can generate noise at those frequencies (as well as harmonics, spurious frequencies, and harmonics of spurious frequencies).