NVIDIA 455 not working properly on Plasma 5.20 (KDE Neon 20.04)

On my KDE Neon 20.04 Testing Edition with 5.8.0-31 kernel & dual 1080p+2160p setup, the display scaled down to 1024x768 and only showed it on my 4K monitor (can’t change the resolution from Plasma’s display settings). I tried opening NVIDIA settings and nothing showed up, either. Reverting back to 450 fixed it.

I’ve seen another report on KDE’s bug tracker that Kubuntu 20.10 (which uses Plasma 5.19) is experiencing issues with 455.

nvidia-bug-report.log.gz (103.8 KB)

Here’s the bug report I posted on KDE’s bug tracker.

System info:
Operating System: KDE neon Testing Edition
KDE Plasma Version: 5.20.4
KDE Frameworks Version: 5.77.0
Qt Version: 5.15.2
Kernel Version: 5.8.0-31-generic
OS Type: 64-bit
Processors: 4 × Intel® Core™ i5-6500 CPU @ 3.20GHz
Memory: 15.6 GiB of RAM
Graphics Processor: GeForce GTX 1060 6GB/PCIe/SSE2

You have a mismatch of kernel and glx modules

Dec 8 01:36:13 Y4M1-MS-7978 kernel: [ 125.033834] NVRM: API mismatch: the client has the version 455.38, but
Dec 8 01:36:13 Y4M1-MS-7978 kernel: [ 125.033834] NVRM: this kernel module has the version 450.80.02. Please
Dec 8 01:36:13 Y4M1-MS-7978 kernel: [ 125.033834] NVRM: make sure that this kernel module and all NVIDIA driver
Dec 8 01:36:13 Y4M1-MS-7978 kernel: [ 125.033834] NVRM: components have the same version.

Please completely purge the current driver and cleanly install the 455 one.

I would’ve thought it’d be looking for the same ones. When I tried again I noticed that linux-module-nvidia-450 packages are left behind, and I thought they were removed when the meta package was removed.

BTW, why were these considered “extra drivers”. What’s the reason to install the Linux module? I was hoping that by installing that, it’d make the splash screen look better, but that didn’t work, and I just didn’t bother uninstalling it.

The reasons are performance, vulkan and cuda. Without the proprietary nvidia driver, the reverse-engineered, open source ‘nouveau’ driver is used which can’t reclock the gpu so is always running at minimum performance.
The splash screen (I guess you mean ‘plymouth’) should rather look better when using nouveau, so there’s something else going wrong.