How do Muslim traders determine what's Halal and what's not?

I've been reading a lot about this recently, and the more I read, the more opinions I seem to find.

Some people say all trading is Haram because it's speculative and resembles gambling.

Others say trading can be Halal as long as it avoids things like:

Riba (interest)

Excessive uncertainty (gharar)

Interest-based leverage

Trading impermissible assets

Then there are discussions around forex, stocks, crypto, futures, CFDs... and everyone seems to draw the line in a different place.

I'm not trying to start an argument or challenge anyone's beliefs. I'm genuinely asking out of curiosity because I'd like to understand how different Muslim traders think about this.

If you're a Muslim and you trade:

What convinced you that your approach is Halal (or Haram)?

Was there a scholar, fatwa, or principle that helped you reach that conclusion?

Did you change your view over time?

I'd really appreciate hearing different perspectives. Please keep it respectful.