A bootable USB allows you to wipe your hard drive and install a fresh copy of macOS Mojave. This resolves performance issues, driver conflicts, and malware.
This is a common certificate expiration issue. Since Mojave is old, the internal certificate has expired. Fix: Disconnect the internet during installation, or run this Terminal command before installing: Download Mac Os Mojave 10.14 6 Dmg
date 0101010119
(Set system date to Jan 1, 2019). After installation, re-enable "Set date & time automatically." A bootable USB allows you to wipe your
If your Mac is older, use DosDude1’s Mojave Patcher (unofficial) – but that requires a custom DMG, not the official one. (Set system date to Jan 1, 2019)
Your Mac is either too old (pre-2012) or too new (2019+ with T2 chip). Mojave does not support Macs released after 2019. Apple Silicon Macs cannot run Mojave at all.