The pirate score sheet says you get one point for every 3000 credits earned "smuggling". Now I suppose
this means buying/selling goods which are prohibited on a specific planet.
If it is so, then is there a way to do it in some other way than the (I feel) awkward "buy/sell illegal goods, then pay money to increase their attitude because otherwise you can't even trade with the planet" method?
I think this way it's not smuggling as they are apparently clearly aware of what you are doing.

Is there maybe a possibility to really "smuggle" goods?

Attitude drop depends on the size of sold contraband, so you can become planet's enemy and get into jail instead of bribe.
Less awkward smuggling:
[begin]
[repeat until out of planets]
"sell 100 narcotics",
"flee from the planet"
"purchase more narcotics"
[/repeat]
"change race on pirate station".
[/end]
It works better after 5-7 years in space, Pelengs sell narcotics for 500, Gaals purchase for 1000.
100 items = 50k gross income, 100k for smuggling.

It is a matter of taste. Imo, system is pretty believable. When government sees that after ship's arrival there is sudden increase of contraband on the black matter, it is common sense to suspect you as smuggler. The bigger the cargo you sell, the more distinctive proofs they get - and more attitude they lose.

What I find funny is that the money you made from the transaction where you got busted isn't confiscated - you get to keep the entirety! Additionally, you could have a cargo bay still full of contraband, and they always let you keep it - waiting for you when you leave jail or escape!

Thing is, illegal for them doesn't mean illegal for neighbours. In real life similar goes about alcohol in muslim countries - it's prohibited, but if you don't sell it, they don't take it from cruise ship.

That's a good point actually. I was just thinking about it in terms of airports/drugs, where just walking in with it gets you arrested. And now that I think about it, I reckon if we got busted for just having stuff in the cargo hold when landing on a planet, then there would be many times I would have been busted by accident...