Input your Apple ID and password (an app-specific password is recommended for safety) to sign the app.
As Apple has added features like dark mode, widgets, and file management, the need for Cydia has decreased. Additionally, Apple's "Rootless" security in newer iOS versions has made traditional Cydia-style jailbreaking much more difficult.
It allows the installation of "tweaks" that change how iOS looks and behaves. cydia ipa file
AltStore is one of the most reliable, free methods for sideloading IPAs. It uses your personal Apple ID to sign the apps, tricking your device into thinking you are testing an app you developed yourself. Download on your Windows PC or Mac. Connect your iPhone to your computer via USB.
If you want (modified apps):
Some tweaked apps (like modified banking apps or social media clients) can harvest your login credentials. Never use tweaked apps for sensitive financial accounts.
You're looking for the Cydia IPA file!
As of late 2019, Impactor typically requires a paid Apple Developer Account to function properly.