Brass and aluminum are both incompatible with stainless steel. Brass is a little less corrosive but the difference is small. Both will corrode and seize, especially if used dry. I’ve tried to work on many wheels with corroded brass nipples. On the other hand, I have lots of wheels with aluminum spoke nipples that have never corroded even when used through many winters.

Spoke preparation and lubrication does help keep corrosion down. Lubrication isn’t there just to make the parts move freely. It’s there to serve as a electron barrier. Just sitting around won’t lead to corrosion. A vehicle to get moisture into the spoke nipple/spoke contact has to exist and a metal to metal contact has to exist. Moisture won’t wick down into the threads if a lubricant is used nor will electrons move if there is a nonpolar layer between the metals.

I wouldn’t suggest using square aluminum nipples for the reasons I’ve given above but square brass nipples are only slightly better. Corrode either because the spoke nipples have been used dry and neither one is easy to work on.