Well, twice now I have stated my recommendation and twice you have asked if you understood them correctly by stating the opposite.
It sounds like you prefer the option to install the proprietary AMDGPU, so I recommend that you test this option first and see if it provides a solution or the results that you need. It very well might and is worth trying.
To do this, I would suggest installing Zorin OS 17 in the normal fasion. On reboot, boot into the Grub Menu, then select the Advanced Options for Zorin and select to boot Zorin on -kernel- (Recovery).
In the recovery menu, arrow key down to Enable Networking. Once enabled, back up to the recovery menu and arrow key down to Root - drop to prompt. From here, follow the steps to install the AMDGPU. In this way, you never enter the desktop to get a blank screen.
Once completed, test booting normally.