Zorin OS 18 Core on AMD A8 APU and AMD RX 460

[Forpli]

Did you check that the cable is well connected on both sides?

In this thread with an RX 470 adding the kernel parameter 'amdgpu.aspm=0' to file /etc/default/grub helped (ubuntu 24.04 based, kernel 6.8):

https://forums.linuxmint.com/viewtopic.php?t=435435

If I were you I'd try the suggestion of Aravisian first

I cant boot my Linux 18 OS

In this line: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" Make it look exactly like: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash amdgpu.si_support=1 radeon.si_support=0 There is one space between each parameter. You can see above that you go from two parameters quiet and splash to Four parameters. Tap ctl+o to overwrite, then enter to save as current configuration. Tap ctl+x to exit the editor. Now run sudo update-grub Reboot and test.

If it doesn't help you could also take a look at this solution:

Ubuntu MATE 22.04 will only boot in recovery mode

Here is mentioned that

GRUB_CMDLINE_LINUX_DEFAULT="radeon.si_support=1 radeon.cik_support=1 amdgpu.si_support=0 amdgpu.cik_support=0 amdgpu.dc=0 amdgpu.dpm=0 amdgpu.modeset=0"

helped for RX 470.

When you try to add the kernel parameters always run the command 'sudo update-grub' afterwards and reboot to apply it. In the linked Zorin-thread you find a guide how to add kernel parameters.