The unc0ver jailbreak, developed by Pwn20wnd, is back in a version 6.0 delivered overnight from Saturday to Sunday. The previous version stopped at iOS 13.5, Apple then corrected the flaw that allowed the tool to unload an iPhone or iPad. We will see how long this new version will last!
In the meantime, unc0ver 6.0 knows how to jailbreak all iPhone and iPad running iOS 11 up to iOS 14.3. The iPhone 12 are therefore included in the batch (as long as they are under iOS 14 to iOS 14.3)! Opposite, checkra1n only supports devices with chips A7 to A11, but it is not likely to be clogged one day since it relies on a hardware flaw. unc0ver exploits a software vulnerability in the iOS kernel. Please note, iOS 14.4 is not supported by unc0ver 6.0.
To install unc0ver, the easiest method is still to go through the AltStore alternative store, which requires a few fairly simple manipulations (read: The jailbreak in 2020, as funny and frustrating as in 2007). A manual for installation via Xcode and Cydia Impactor (the latter requiring an Apple developer account) can be found on the unc0ver site.