Plz tell me how
An admin on the wiki can install https://dev.fandom.com/wiki/WallGreeting
Or you could install it to your personal JS if you just want it for yourself.
But then you will be the only one who see the greeting, which pretty much counters the point of a greeting.
If the goal is to have your own greeting, yes. However, I install it in my personal JS so I can see the legacy greetings on any wiki I visit.
What do you think?