Hi,
My Vero 4k Power Supply makes strange noise. Like coil whine. Is it still save to use?
Hard to say but better to replace it:
You can grab them here;
Specification: DC 5V, min. 2A, center positive, coaxial power connector male with OD 5.5mm and ID 2.1mm. Don’t use wall adapters designed for charging since they do not provide a stable voltage.
If it is just coil whine by itself then there should be nothing unsafe about it. It is an annoyance, but it is just wires vibrating and not uncommon, generally speaking, in electronics. If the connected device becomes unstable, or the power supply exhibits any kind of unexpected odor (any burnt smell in particular), then it should no longer be trusted.