If your console is on a version lower than 9.00, you can update manually. If you have already updated past 9.00, you cannot "downgrade" to this version using software alone. Getting Started - ConsoleMods Wiki
The Golden Threshold: PS4 Firmware 9.00 as a Case Study in Digital Preservation and Exploit Economics ps4 9.00 firmware download
When Sony pushed System Software 9.00 in December 2021, the patch notes were mundane: “Improved system performance.” Under the hood, however, it introduced a WebKit vulnerability (CVE-2021-44529) and a BD-JB (Blu-ray Disc Java) exploit that, when combined, offered kernel-level access. Unlike previous exploits (e.g., 5.05’s “Mirage” or 6.72’s unstable chain), 9.00’s method was novel: it required a simple USB exFAT drive as a “jailbreak key.” This hardware dependency, while quirky, made the exploit more reliable than software-only attacks. If your console is on a version lower than 9