Most people use the computer method of manually signing apps and people that are lucky enough to have an official apple dev certificate/account may use Cydia Extender but today I'm showing you how to get Cydia Extender on any iOS. Of course, you need to be jailbroken for this. These simple steps allow you to sign apps manually and automatically, making it so you don't need to sign again every 7 days manually.
Set-up:
1. Add the following repo to Cydia/Sileo:
"https://julioverne.github.io"
Steps:
1. Install "Ext3nder Installer" from the repo you just added
2. Respring
3. Open the Extender app then go onto (the app's) settings, scroll down and add your apple info in (account must not have 2FA)
4. Once you download any ipa, just open it in Extender and it installs/signs itself or you could make it auto-sign existing apps.