ThinkPad T450s with whitelist for displays removed: how to get rid of the 5 beeps of doom

I had a ThinkPad T450s with a broken display. I replaced it with a display out of a T14. Obviously the EDID of this new display is not in the whitelist of the T450s. So I couldn’t adjust anymore the brightness in Windows with F5/F6.
Following the tutorial “Tutorial: T450/T450s/W550s/T550/X250 Screen Whitelist Removal” I modded the BIOS. This worked out very well, but now I got a beep concert at every cold start because of broken checksums.
I found another tutorial which described in detail how to get rid of this beep concert for a Lenovo L440 “”[GUIDE] Fix Insyde H2O BIOS signature (5 beeps on Lenovo)".
Following this tutorial as close as possible I tried to do the same for my modded BIOS, but I failed. The laptop didn’t boot anymore.

What has changed from the ThinkPad xx40 series to the xx50 series? How can I adapt the procedure described in the tutorial to a T450s? Any tipp greatly appreciated.

P.S.: sorry for not posting the links to the tutorials, but the forum SW tells me: New members need a minimum of 3 posts before posting external links