My last update has left me with black screen and had to switch to Plasma X11

After sleeping on it I have the following:-

alastair@HP-Z640-1:~> inxi -Gaz
Graphics:
  Device-1: Advanced Micro Devices [AMD/ATI] Ellesmere [Radeon Pro WX 7100]
    vendor: Dell driver: amdgpu v: kernel arch: GCN-4 code: Arctic Islands
    process: GF 14nm built: 2016-20 pcie: gen: 3 speed: 8 GT/s lanes: 16
    ports: active: DP-4 empty: DP-1,DP-2,DP-3 bus-ID: 02:00.0
    chip-ID: 1002:67c4 class-ID: 0300 temp: 46.0 C
  Display: wayland server: X.org v: 1.21.1.15 with: Xwayland v: 24.1.8
    compositor: kwin_wayland driver: X: loaded: modesetting unloaded: vesa
    alternate: fbdev dri: radeonsi gpu: amdgpu display-ID: 0
  Monitor-1: DP-4 model: Asus PB258 serial: <filter> built: 2015 res:
    mode: 2560x1440 hz: 60 scale: 100% (1) dpi: 118 gamma: 1.2
    size: 553x311mm (21.77x12.24") diag: 634mm (25") ratio: 16:9 modes:
    max: 2560x1440 min: 720x400
  API: EGL v: 1.5 hw: drv: amd radeonsi platforms: device: 0 drv: radeonsi
    device: 1 drv: swrast gbm: drv: kms_swrast surfaceless: drv: radeonsi
    wayland: drv: radeonsi x11: drv: radeonsi
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: amd mesa v: 25.2.4 glx-v: 1.4
    direct-render: yes renderer: AMD Radeon Pro WX 7100 Graphics (radeonsi
    polaris10 ACO DRM 3.64 6.17.1-1-default) device-ID: 1002:67c4
    memory: 7.81 GiB unified: no display-ID: :0.0
  API: Vulkan v: 1.4.328 layers: 1 device: 0 type: discrete-gpu name: AMD
    Radeon Pro WX 7100 Graphics (RADV POLARIS10) driver: mesa radv v: 25.2.4
    device-ID: 1002:67c4 surfaces: N/A device: 1 type: cpu name: llvmpipe
    (LLVM 21.1.3 256 bits) driver: mesa llvmpipe v: 25.2.4 (LLVM 21.1.3)
    device-ID: 10005:0000 surfaces: N/A
  Info: Tools: api: eglinfo, glxinfo, vulkaninfo
    de: kscreen-console,kscreen-doctor wl: wayland-info
    x11: xdpyinfo, xprop, xrandr
alastair@HP-Z640-1:~>

The symptoms from last night were black screen as before but with mouse working.
I also have:-


alastair@HP-Z640-1:/etc> cat nsswitch.conf
#
# /etc/nsswitch.conf
#
# An example Name Service Switch config file. This file should be
# sorted with the most-used services at the beginning.
#
# Valid databases are: aliases, ethers, group, gshadow, hosts,
# initgroups, netgroup, networks, passwd, protocols, publickey,
# rpc, services, and shadow.
#
# Valid service provider entries include (in alphabetical order):
#
#       compat                  Use /etc files plus *_compat pseudo-db
#       db                      Use the pre-processed /var/db files
#       dns                     Use DNS (Domain Name Service)
#       files                   Use the local files in /etc
#       hesiod                  Use Hesiod (DNS) for user lookups
#       nis                     Use NIS (NIS version 2), also called YP
#       nisplus                 Use NIS+ (NIS version 3)
#
# See `info libc 'NSS Basics'` for more information.
#
# Commonly used alternative service providers (may need installation):
#
#       ldap                    Use LDAP directory server
#       myhostname              Use systemd host names
#       mymachines              Use systemd machine names
#       mdns*, mdns*_minimal    Use Avahi mDNS/DNS-SD
#       resolve                 Use systemd resolved resolver
#       sss                     Use System Security Services Daemon (sssd)
#       systemd                 Use systemd for dynamic user option
#       winbind                 Use Samba winbind support
#       wins                    Use Samba wins support
#       wrapper                 Use wrapper module for testing
#
# Notes:
#
# 'sssd' performs its own 'files'-based caching, so it should generally
# come before 'files'.
#
# WARNING: Running nscd with a secondary caching service like sssd may
#          lead to unexpected behaviour, especially with how long
#          entries are cached.
#
# Installation instructions:
#
# To use 'db', install the appropriate package(s) (provide 'makedb' and
# libnss_db.so.*), and place the 'db' in front of 'files' for entries
# you want to be looked up first in the databases, like this:
#
# passwd:    db files
# shadow:    db files
# group:     db files

passwd:         compat systemd
group:          compat [SUCCESS=merge] systemd
shadow:         compat systemd
# Allow initgroups to default to the setting for group.
# initgroups:   compat

hosts:          files mdns_minimal [NOTFOUND=return] dns
networks:       files dns

aliases:        files usrfiles
ethers:         files usrfiles
gshadow:        files usrfiles
netgroup:       files nis
protocols:      files usrfiles
publickey:      files
rpc:            files usrfiles
services:       files usrfiles

automount:      files nis
bootparams:     files
netmasks:       files
alastair@HP-Z640-1:/etc>

which leaves me none the wiser but am still hoping I can identify the underlying issue.

Edit by Sauerland: Code-Tags