Installing Certificates - chillboi20/LegacyiOSGuide GitHub Wiki

Installing certificates can allow you to connect to more online features, since older versions of iOS are too old to have modern certificates authorities trusted. You install certificates by visiting a website on your the device itself, then installing and trusting the certificates.

Do this at your own risk, however, as quoted from IPG's website:

"Please try to remember that I'm a random person on the internet, and always be diligent before blindly trusting something like an SSL certificate from an unknown website."

You can install certificates from http://tlsroot.litten.ca. ISRG Root X1 CA fixes adding repos, and is needed for TubeRepair on iOS 5, while the DigiCert certificates fix logging into iCloud and other Apple services. I recommend to install all the certificates just to be safe.