There is no official version of for the PSP or PPSSPP emulator. While fans have long requested a portable version, the series was never natively released for the PlayStation Portable platform.
: Some users use PC emulators for Android (like Winlator) to run the original PC version of Warband directly on high-end smartphones. Recommended Alternatives on PPSSPP
Why wasn't it on PSP? The original Mount & Blade (2008) and Warband (2010) required complex physics calculations for directional combat, ragdoll physics, and rendering dozens of simultaneous AI agents on a battlefield. The PSP’s 333 MHz CPU and 32 MB of RAM simply could not handle the "hundreds vs. hundreds" battles that define the series.