iPhone 6s iOS 13.3.1 Jailbreak
If your iPhone 6s or iPhone 6s Plus is jailbroken or you want to jailbreak your phone, you'll probably want to stay put on on your current version of iOS for now.
Jailbreak developers have released tools that are compatible with newer versions of iOS 12. You can learn about them right here.
They've also released a jailbreak tool, dubbed checkra1n, that works with iOS 12.3-iOS 13.3 and the iPhone 6s and iPhone 6s Plus. That said, the jailbreak is still in beta and it's unclear if it works with iOS 13.3.1.
For more on the iOS 13 jailbreak, head here.