AMD and Nvidia. That is quite a combo...
The normal solutions of "nomodeset" would do little good as without an intel Graphics card to fall back to, it must have the Nvidia Drivers already in place at init.
What you may need to do is boot, then drop directly to the Recovery menu and from there to Enable Networking. Once you enable networking, bump back up to the Recovery Menu and arrow key down to drop to prompt.
From the Prompt terminal, locate the file 20-intel.conf or similar that should be in /usr/share/X11/xorg.conf.d/ and rm that file. (If you do not have the locate command, you can install it with sudo apt install mlocate). For example:
rm /usr/share/X11/xorg.conf.d/20-intel.conf
Once done, still in the Prompt Terminal, add the repo:
sudo add-apt-repository ppa:oibaf/graphics-drivers
Then
sudo apt update && sudo apt full-upgrade
lastly (optional but worth trying) LightDM does a Much better job of handling Nvidia at init than GDM3 does. You may try
sudo apt install lightdm
and follow all the prompts.
Once done, please try booting into your desktop normally.