This isn't as easy as you'd think.
XLR is a balanced audio signal. The signal is split into two, and one is inverted. The original signal is sent on one wire, the inverse on another wire. At the other end, the inverted wire is inverted again to regenerate the original signal. But this also inverts any noise that was picked up along the length of the cable. When you add the two signal lines together, you get 2x the original signal, and the noise (because one was inverted) cancels out. This is how you have long lengths of unshielded microphone or speaker cable without picking up noise, static, or hum.
There are straight XLR to 3.5mm adapters which bypass all this and simply hook up the positive terminal on the 3.5mm plug to the positive (uninverted) wire on the XLR side.
https
/www.amazon.com/LyxPro-Impedance-Matching-Transformer-Female/dp/B01JZXIIWE
These will work for short lengths where noise isn't a problem. But you may still encounter problems with an impedance mismatch or incorrect signal level. It also won't (or at least shouldn't) work in reverse (3.5mm signal to XLR). In addition, the types of microphones plugged into XLR cables usually need power, and draw it from the XLR cable. So the other end of the cable needs to supply that power, which it won't if you plug it straight into a 3.5mm jack. This is why you're reading that you need some type of mixer.
So if
■you're using an XLR mic which doesn't need power or accepts batteries for power
■its impedance and line level matches what the 3.5mm port is expecting
■and the cable run is relatively short so noise isn't an issue
then you could use a simple adapter like the one above. Otherwise you're going to need a mixer, or if there's some way to get line out from the Scarlett (maybe the headphone direct monitor jack) you could simply plug that into your PS4.