Here are the latest instructions to install Spike to your iPhone.
They'll likely be converted to a forum post instead of a PDF soon.
"Spike-XCode.pdf" is for deploying through MacOS.*
"Spike_Windows.pdf" is for deploying through Windows.
Other install methods, such as Cydia Impactor, are no longer available.
Please note that using these instructions, or portions thereof, is at your own risk. And so is using Spike to begin with.
* = Experimental document for XCode 15 + Apple Configurator, since Apple killed the direct way.