Downloading commercial PS2 games for free—even compressed versions—is generally copyright infringement , unless you own the original disc and are making a personal backup (which anti-piracy laws in many regions still restrict). Abandonware is rarely legally "free" unless the publisher explicitly released it.
When people say "portable," they usually mean playing on a laptop, a Steam Deck, or an Android phone (using AetherSX2 or NetherSX2). ps2 highly compressed games free download portable
1. Technical Overview: Compression and Portability a Steam Deck