iMac Late 2013 27“ won’t boot from 3. Party SSD

Hi guys, I got a free iMac Late 2013 27" that came with a HDD. I had to remove the hard disk for destruction. So I disassembled the iMac, installed a third party nvme ssd with adapter and realized that the firmware is too old to boot from. The hard drive was recognized by the Sonoma installer I created with OCLP, but the installer with the grey hdd icon did not show up even after many attempts.

I read on the internet that firmware can only be updated with original Apple SSDs. Luckily, I still had one lying around from a 2015 MacBook Pro that I successfully upgraded.

So I took the damn thing apart again, installed the original SSD and finally I was able to install Sonoma and boot normally. Now I have installed the third party ssd again and the same problem persists.

I actually wanted to use the Mac for Linux, but even there, I can't boot.

Please save me from wasting countless more hours. I hope you can help me.

submitted by /u/Long_Ad_4906
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