This doesn't work without a $99 developer certificate when you get to the Cydia Impactor step
And if you have an iPhone X or older (iPhone 8, 7, etc) you have a hardware exploit and can jailbreak using checkra1n with just a computer and a USB Lightning cable: https://checkra.in/
Here's a video demo (not mine) of how the AltServer method should work for you: https://twitter.com/InvoxiPlayGames/status/12129681066095656...
You can jailbreak with unc0ver in 3 different ways, one of which requires an Apple Developer account, yes.