Most forms of casino gambling except card games are purely random: dice, roulette, slot machines. I agree with you that there being an element of skill or knowledge doesnt stop it being gambling however.

But that is what the whole discussion is about. Many scenarios aren't just gambling because they have a degree of predictability to it: poker, stock market, betting on the day when the US starts WW3.

Probably only quantum processes are truly random, but for this argument, processes are practically random if the governing variables are not human-knowable. A dice throw, roulette, lottery numbers drawn from a bowl. They are deep down deterministic, but not predictable to any degree.