I myself haven't used anything other than brass cases in my handguns. I did try aluminum 1 time over 10years ago(45acp) and that didn't work out. Nothing but ejection issues. I do however use steel cases in my ar15s with zero issues and will continue.Nickel is magnetic also. It doesn't mean they are steel cases coated in nickel.
There is Tula Russian brand or was Russian called Sargent Major that is Zinc coated steel.Well yeah as far as I know Russian stuff is just steel case. Maybe they are coating it with brass now. I think there is a ban on Russian ammo right now anyway. Seems like Silver Bear might have been zinc plated steel.
I have seen some silver and brass colored coated steel cases around. I think there was a guy on this forum that tried reloading steel case for a while. Seems like high risk and low reward to me.
I've reloaded 4x on Blazer aluminum. On the 4th time I had maybe 2 out of 100 split on me. It was am experiment to see if they could indeed be loaded if necessary.What happens when you reload an Aluminum case? I did one by accident, was told by my gray beard reloader mentor that it's not good. We fired it. It went bang.