Lubuntu 20.04.2 LTS - artefacts issue on log in screen after log out from the session

[Piotr]

Dear Lubuntu Developers,

I used live USB with Lubuntu 20.04.2 LTS and I found very serious bug. After log out from the session we can see screen where we must type password to log in. In this screen I noticed a lot of issues with artefacts when I moved my mouse cursor. My display was blinking and white arfefacts are showed. I don't know if it is common issue. Someone use Lubuntu 20.04.2 LTS and can tell me if only I have this problem or this is common issue?

My distro: Lubuntu 20.04.2 LTS without update (live USB for testing, clean iso)
My VGA: [AMD/ATI] RV516/M64-S [Mobility Radeon X2300]

lshw -c video
 description: VGA compatible controller
       product: RV516/M64-S [Mobility Radeon X2300]
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       configuration: driver=radeon latency=0

I hope that you fix it quickly.

Yours faithfully,
Piotr

[Chris Guiver (guiverc)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please execute the following command only once, as it will automatically gather debugging information, in a terminal:

apport-collect 1927791

When reporting bugs in the future please use apport by using 'ubuntu-bug' and the name of the package affected. You can learn more about this functionality at https://wiki.ubuntu.com/ReportingBugs.

From your description this reads like a duplicate of issues that occur at the greeter or `sddm` which is not unique to Lubuntu, however without a picture I cannot confirm this.

Please check out https://bugs.launchpad.net/ubuntu/+source/sddm/+bug/1865837 and if it matches, please say so, or mark this report a duplicate of that report (there are others too that also fitted this description, but that is a like radeon card..)

[Piotr (peterq94)]

@Chris Guiver this looks that this is the same bug. So why you didn't fix it yet? This is old bug. It still affected Lubuntu 20.04.2. I can fix it myself with installing other package? Why you didn't change display manager if sddm have problems? Is this package from LXQt or what is the problem?

[Chris Guiver (guiverc)]

Lubuntu is better using `sddm` in my opinion than swapping out that DM for another just because currently five people have tagged "affects me too" (including me too).

The issue can be mitigated; if I recall correctly, I've used it as example of how to on Lubuntu's discourse, which to me is a more appropriate fix for the issue (given it impacts so few boxes; just those with specific radeon & I used with an intel card).

(other issues appeared with the 5.3 kernel used by 19.10 that had a like effect impacting nvidia cards.. It's better for everyone if 99% of users are using the most efficient DM (`sddm`) for Lubuntu, and the few impacted by strange graphic glitches switch out if they deem it necessary.

On my optiplex 755 I resolved the issue by changing login themes (sample a few before I got one I liked & it had no glitches, but it was my solution, but its not the only fix).

I'm not personally sure it's a `sddm` issue anyway, more `sddm` is causing graphic glitches & the bug is actually in the 'driver' or kernel module... why it appeared in 5.3/19.10, but I'm guessing.

Lubuntu is a small team, and we don't have resources to find & fix it; and as I already stated, I don't think swapping `sddm` to another DM is a wise move.

Thank you for your last comment, I'll mark this a duplicate.

Thank you for taking the time to report this bug and helping to make Lubuntu better.

[Piotr (peterq94)]

I noticed this same bug in Lubuntu 21.04 (hirsute hippo). Is better because you removed themes but bug still exist. I noticed also that I can't choose language on boot screen? This doesn't work on 21.04?

[Piotr (peterq94)]

This same bug also exist in Fedora 34 Spin LXQt where we have LXQt 0.16.0 so this is not problem only with Lubuntu. Have you sure that this is problem with sddm?