Ours was organised by the company who manage the building, it was the same at our previous apartment. We were billed for the name plate and the engraving both times, it was about 30 francs.
When I moved in my current apartment I put stickers, and after some time I received a (gentle) letter from the administration asking me to fill a form and order proper labels like the others.
If most or all the others have plain stickers, or if you're the only one, then ok
Pas de Pub! Probably something different in Zurideutch. Those you can get at the supermarkets . Not 100% effective as people paid to stuff mailboxes just ignore them, but the Post will stop delivering junk mail.
Is it a house or an apartment? I have not lived in an apartment in decades, but in both cases when I did the one landlord took care of the name plates himself and the other required you to get them from a specific supplier as the both wanted all the names of the boxes to be in the same style.