Comparison between Raspian 12 Bookworm on Raspberry Pi 4 and Raspberry Pi 5

That's the problem, the config file is not in the /boot folder. I created a new one with the SPI=on instruction and it doesn't even work. I don't know if this config file is not in /boot but in another subdirectory.

The config.txt is not directly under boot, its there you'll have to look you don't need to create one. Have a look under /boot/broadcom