JurassicTurd

I would like to Jailbreak my device with the unc0ver Jailbreak but need an older IOS version. I have looked by myself for different ways to downgrade or rollback my IOS to 14/13 and cannot find any successful methods. I have read that the older versions aren't signed anymore so we cannot downgrade to them. I am not familiar with what exactly that means and still would like to know if there is a workaround for downgrading to a non-signed IOS versions.