Hello and welcome,
LFLs on private property are not allowed, and if you do come across one, you should request removal. I have had to have several LFLs on PRP removed, as most are actually on the front lawn permanently, or in a large planter, if it’s not allowed to dig a hole in the area.
Now, it does depend on the country, but at least in the US, most sidewalks are part of the property, if maintained by the local government. The property typically ends at the street berm, not the sidewalk. This mini golf course actually looks to be on the private property, not the sidewalk; it’s right off of the sidewalk, but it’s location still makes it ineligible.
We also have more info on PRP, our shorthand for private property, here: