Hollow Knight is several gigabytes. A PSP ISO cannot exceed 1.8 GB due to UMD disk limits.
The safest homebrew projects are hosted openly on GitHub, where you can see the developer's updates and patch notes directly. hollow knight psp iso updated
While the idea of pulling out a dusty PSP to explore the depths of Hallownest sounds amazing, the hardware simply cannot support it. If you download a file, expect either a very basic, short fan-made homebrew demo, a reskinned retro game, or a mislabeled file meant for a different console. Hollow Knight is several gigabytes