SUMMARY
*Ubuntu AMD Radeon driver (also for Kubuntu) crashes login/keyboard.

STEPS TO REPRODUCE
1. Install *Ubuntu AMD Radeon driver installer package .deb (repo.radeon.com. dpkg -i package.deb.)
2. Root text-edit (such as with emacs, mcedit, micro, nano, pico, vi) /usr/bin/amdgpu-install to add 'neon|' in front of 'ubuntu|linuxmint|debian' (about line 294.)
3. Install drivers such as: amdgpu-install --opencl=rocr,legacy --no-32 --accept-eula.
4. Reboot.

OBSERVED RESULT
*Ubuntu AMD Radeon driver (also for Kubuntu) crashes login/keyboard: disabled except software keyboard--though almost no one would know--one can use mouse to select button to reenable hardware keyboard, then an error displays (below) and can't login.

        The current theme cannot be be loaded due to the errors below, please select another theme.  file:///user/share/sddm/themes/breeze/Main.qml:12.1:plugin cannot be loaded for module "org.kde.plasma.core": cannot load library /usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/core/libcorebindingsplugin.so: (/lib/x86_64-linux-gnu/libKF5GuiAddons.so.5: undefined symbol: wl_proxy_marshal_flags.

EXPECTED RESULT
Never replace desktop hardware with software keyboard when there's no touchscreen!  Don't have theme-dependent login.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE Neon 5.25 GNU with testing on Linux 5.15.0-42-lowlatency, some of 5.4.0-122-lowlatency, 5.8.0-63-lowlatency, 5.11.0-46-lowlatency, 5.13.0-51-lowlatency, 5.15.0-42-lowlatency (and some such generic kernels.)
KDE Plasma Version: 4:5.25.3-0xneon+20.04+focal+release+build58
KDE Frameworks Version: 5.96.0
Qt Version: 5.15.5

OTHER INFORMATION
hardware: ASUS Tuf Radeon RX 5700 XT, Sapphire AMD Radeon RX 580.
I hope I typed the error right and could (with instructions) copy error message from log file or photograph screen.