The HP 255 G6 (AMD) Linux hack/workaround page

Usually these are just kernel parameters and should only be from value when running older Linux kernels. Any Linux distribution having Linux kernel 5.0.1+ inside should work without any problems. When I got this laptop brandnew some drivers that are necessary to run this machine properly weren't working or not included at all. This shouldn't be a problem when running newer kernels as stated above.

The laptop is freezing on shutdown and the caps lock LED is blinking or the same does happen without a blinking LED

This issue seems to occur on kernels older than 4.19. Just append amdgpu.dc=0 to your kernel parameters. Note that using this kernel parameter on newer kernels can cause your screen backlight to stop working which means you should remove it. Also the screen turning blank and on-off three times and light graphic glitches are normal using this kernel parameter. These will go away once the system is fully booted.

The above kernel parameter is not working for me

Then use a newer kernel. Consult your distribution's manual or community forums to find out how to do this. By now every major distribution should ship with a new enough kernel to support this laptop properly.