Mac stuck at the loading bar, when trying to boot from macOS Catalina Patcher
Now I deleted the patcher and everything related to it from the machine. Then re-download the tool and also created the bootable USB drive again. I was able to boot from the drive and also install Catalina. But the MacBook again hang at nearly 100%. Then I restarted the machine and the setup dialog appeared! Yes, my MacBookPro8,1 is supported!
As an alternative I'd have tried another patcher.