This video covers installing or upgrading to ARK4 custom firmware for any PSP as of July 2024.
100% online method. No PC required.

Learn how to:
Direct download tools from http://psp.lusidgames.com using the PSP web browser
remove infinity and any old CFW by doing a clean install of 6.61 with chronoswitch
Run Ark loader
Run Ark Full Installer
Run cIPL flasher, compatible with all PSP models
Import classic plugins into ark plugin manager
register new plugins with the ark custom launcher
perform an online update to the latest Ark4