The first stage is the filtering stage, where the input power is filtered. Input filtering stage is important as components here protect you from voltage surges and generated interference. The filtering stage in this PSU starts right at the AC socket, where we have a small PCB holding 2 Y capacitors (blue), 1 X capacitor (yellow) and 1 ferrite coil.
On the main PCB however, we have very few components for this stage. All I could identify was an NTC (green in color), which limits the inrush current at the time of charging of the primary capacitors. There were 2 MOVs hidden behind those capacitors, not visible in the image.
Overall this stage is fine, its got almost all recommended components and I don’t have much to complain about here.