Why does it do this?

It's because the charger has a low impedance and because the prongs in the plug or the contacts in the outlet are dirty, corroded, worn or loose.

Is this a normal behavior?

No it is not normal, but it isn't especially rare.

Is it not?

Yes it is not.

Can this damage the charger, laptop or electrical installation?

It is unlikely to cause damage to the charger or the laptop. Sparking can erode the contacts (plug pins or outlet contacts) but this is a minor problem if it only happens when you initially push the plug in.

Is it safe?

Nothing in life is safe, there are only degrees of safety. Sparks can set fire to things. Sparks are a possible symptom of a bad contact that may be causing heat that can lead to failure or fire. it is preferable (and safer) to have connectors that don't cause noticeable sparks.

Since you are concerned and outlets and plugs are cheaper than today's lunch, I would replace both.

It is normal. I live in Europe too and got my electricity checked a while ago. The chargers don't have an off and on switch so the electricity bursts from the outlet to the charger. Don't worry the plugs are made from special material that stops electricity from shocking you.

The Arc is also a result of the high inrush current. Laptop supplies have a flyback converter. The AC grid voltage is first rectified followed by a capacitor. During plug in this capacitor is empty and has very low impedance, so a very high inrush current. The current depends on the moment you plug in: during a zero crossing of the voltage will give very low current while plugging in at the top of the sine, you have max inrush current and max arc.

This may be already solved, but I do have some experience with this. I'm from America (Not USA, but Latin America) and while the power is different from Europe, I did have something similar happen to my laptops for sometime.

I figured out that the way to stop this from happening was to plug-in the power supply first into the Laptop and then connect the prongs into the electrical lines, therefore grounding it with metal. While it may not stop the electrical surge, it's better incase you are worried about a fire or a shock to yourself.

Its certainly not "normal" to always get a (visible) spark, upon plugging in an appliance.

I have a ton of appliances and electronic gizmos that I plug in and plug out regularly.

Out of all these, ONLY the Lenovo power supply of my Yoga 920 laptop causes a pronounced, bright and noisy spark every time I plug it in, no matter if at home, in a hotel or wherever. It has done this since I first unpacked it.

I think that is poor construction. At least, they provided a grounded PSU, so I don't get shocks upon touching the metal surface of the laptop, unlike my Aorus gaming laptop, which also had a metal laptop case, but no grounded PSU. The surface always felt "alive" because of that, and the black anodization started to come off over time in the areas where my palms were touching the case...