Chimera failed on iPad Mini 2 (12.5.7)

I'm trying to jailbreak an old iPad Mini 2 (ME276NF/A) running iOS 12.5.7 with Chimera, using the steps from https://ios.cfw.guide/installing-chimera/

Sideloading Chimera worked without issues. When trying to run it, first it kept rebooting without any message and now I'm getting the message "An Error Occurred. Your device could not be jailbroken because the exploit failed."

What are the steps I could take to solve this?