As you probably already know, this question is usually about the fact that aluminum is chemically more reactive than stainless, so that certain chemical conditions in the pot can rise to having traces of aluminum compounds in your mash. Up until abouut 10 years ago, I did almost all of my distilling in aluminum pots, and much of the mashing.
To prove to myself that it was ok, I searched the web pretty exhaustively to see if any volatile, that is to say “capable of being evaporated”, aluminum compounds known to chemistry. The only ones that I found were lab curiosities, that could only be made in a lab under very difficult to achieve conditions. My point in this is that if the aluminum compounds can’t become vapor, they’ll never come across with the vapor in a still.
That doesn’t mean I’d brew beer in aluminum, but it’s ok for stilling. Some people will object to this, but often they are people who drink highly-acidic soft drinks from aluminum cans,