Newark has a new Priority Pass lounge: the Air Canada Maple Leaf Lounge, which opened last fall.
The lounge is open 4:30-15:30 and airside, meaning you need to pass through security. Security is that pier is a bottleneck so I would not bother visiting unless flying out of there. In many cases you’ll do better visiting the Art & Lounge outside security in Terminal B.
Air Canada is marooned in a dreary pier of Terminal A. If you think Newark is dumpy you have you only experience Terminal B & C, this is a another few rungs down. It is populated by several US airlines. In building a lounge, I guess Air Canada has given up relocating somewhere better.
Readers, have you visited? How is it?