SUMMARY

Hello everyone, I was installing a flatpak application from the Discover store, when I noticed some issue related to OpenGL, after which I stopped the installation and installed some other apps. After doing a restart I notice, I could not see plasma desktop and is with a blank screen and the mouse cursor moving, something like there was no taskbar, no home button, no desktop, etc. I asked few people for help in a chatroom and got to know about some mismatch in the software installed, something related to software version having mismatch with neon's (specifically, issue looked to be incompatible versions of libraries and applications installed Cannot mix incompatible Qt library (5.15.9) with this library (5.15.10)). So, after deliberate fixing of those mismatch issues, rectifying dependencies and doing the installation of neon-settings2 which was creating issue. Finally, I was able to update the system using pkcon update command, and I was able to see my desktop. But there was a critical issue of "Red color on screen" everywhere, even in web browsers and apps. So, I tried to investigate this issue and got to know that during the update the graphics drivers were updated to the latest intel mesa version, which was creating these issues. So, I tried to downgrade the graphics driver and its related packages so check whether the issue persists or gone. To my surprise, the red color issue was gone, and then I noticed that the OS has changed the graphics accelerator to LLMpipe instead of OpenGL, which was confusing to me. At this time I got to know about a BUG (bug #460404) in KDE plasma, which said to change the option to OpenGL in the plasma renderer settings (SceneGraphBackend), and when I did that, still the OpenGL is not working and the software rendering of LLMpipe shows. I tried to check the booting process, and it showed software renderer (LLMpipe) instead of intel drivers. I have manually used the plasma renderer setting (SceneGraphBackend) to software mode rather than OpenGL mode, because if I update the system and new drivers get updated, then that could create a crash or something which I suffered earlier. Please kindly provide a fix to this graphics drivers issue, for which I would be indebted to you.

Thanks & Regards,
Gourab
  
STEPS TO REPRODUCE
1. Had overriding issue + unmet dependencies, fixed those first
2. Did system update using Pkcon update, was successful, but after restart had drivers issue with Red color everywhere
3. Downgraded the graphics driver, and its related packages to make the graphics work, but rendering happened for software (LLMpipe) mode only, even after manually changing the plasma renderer settings (SceneGraphBackend) to OpenGL, still it remained as (LLMpipe) mode.
4. Till now, I have kept the plasma renderer settings mode to software (LLMpipe) mode, so that whenever I update the system and graphics drivers are updated, it won't break my system again. 
5. Please provide compatible graphics drivers for my system.

OBSERVED RESULT
1. Red Color everywhere on the screen
2. System responsive with software rendering (forceful)
3. workable for now, but drivers update may crash the system again

EXPECTED RESULT
1. Intel drivers should have been showing during boot logs
2. Graphics hardware acceleration must have been worked using OpenGL settings, even after drivers update
3. Stable system that would not crash after update

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE Neon 5.27
(available in About System)
KDE Plasma Version: 5.27.7
KDE Frameworks Version: 5.109.0
Qt Version: 5.15.10
Kernel Version: 6.2.0-32-generic (64-bit)
Graphics Platform: X11

ADDITIONAL INFORMATION
Processors: 4 × Intel® Core™2 Quad CPU Q9400 @ 2.66GHz
Memory: 3.8 GiB of RAM
Graphics Processor: llvmpipe
Manufacturer: Hewlett-Packard
Product Name: HP dx2480 MT