The item associated with the alternator that can cause ripple when bad does not cause squeal. Squeal is caused by slippage, and that’s caused by a worn/loose/stretched belt or a component starting to fail and binding. The component could be the tensioner, the AC compressor, the power steering pump, and yes, the alternator.
Ripple is caused by a bad alternator, specifically a diode in the bridge rectifier.
Since the sqeal was happening before the alternator was changed, I suspect you have something else failing. With the belt(s) removed, try turning and laterally wobblilng every driven pulley to see if you can find a component going bad. Check the tensioner (a Haynes manual will tell you how and what tool you need…it’s not expensive).
The alternator itself can be bench checked. Have that done by the place where you bought it.