Maybe instead of wasting money trying to come up with skate deterrents that won’t work (you think you made it unskateable but skateboarders will then see a different way to use it) how about we start going in the direction that Europe has been going in. In places like Paris, Bordeaux, and Barcelona, they have actively been adding skate obstacles into public parks and around their cities. With skateboarding gaining more and more popularity over the years and with it now being in the Olympics, you will only see more kids/adults picking it up (I have meet many people in their late 20s,30s, and 40s at Apex skatepark who have just started) and as someone who has skateboarded for over 21 yrs, I can assure you that people will find a way to skate there.
Skateboarding started by skating in city streets and in public areas. skateboarders will always be drawn to interesting architecture, I am by no means saying that it is right to skate on public property, but in the skateboard community they will always want to skate a street spot over a generic skate park. For example Marsh Creek skatepark in Raleigh, was labeled a, “certified piece of suck”, by Thrasher Magazine (largest skateboard publication). It is still the only park in Raleigh.
Just my two cents, I’m sure people on here will disagree and I understand that.
See examples below of what Europe has been doing: