[Bug 1939222] Re: DisplayPort over USB-C not working after release update

Could you try 5.13 kernel too?
https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.13/amd64/

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https://bugs.launchpad.net/bugs/1939222

Title:
DisplayPort over USB-C not working after release update

Status in linux package in Ubuntu:
Confirmed

Bug description:
After (automated) update from 5.8.0-63 to 5.11.0.-25 the displayport over usb-c (Thinkpad e15gen2 i5-1135G7 / GeForce MX450/PCIe/SSE2) is not working properly.
Revert to 5.8.0-63 resolves the problem.
The problem is independent of nvdia-drivers (tried 470, 460 and intel only drivers). Same Monitors connected over HDMI work properly. Problem is limited to displayport over usb-c.

Problem symptoms: Monitor atttached over displayport allows only VGA resolution(1024 * 768) and
flickers (on/off periodically).

no special error messages found in dmesg except for abundance of
"i915 0000:00:02.0: [drm] *ERROR* failed to enable link training"

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.35
ProcVersionSignature: Ubuntu 5.11.0-25.27~20.04.1-generic 5.11.22
Uname: Linux 5.11.0-25-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu27.18
Architecture: amd64
CasperMD5CheckResult: skip
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Sun Aug 8 09:12:10 2021
InstallationDate: Installed on 2021-06-14 (54 days ago)
InstallationMedia: Ubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
PackageArchitecture: all
ProcEnviron:
LANGUAGE=en_IL:en
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_IL
SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
Symptom: release-upgrade
UpgradeStatus: No upgrade log present (probably fresh install)
VarLogDistupgradeTermlog:

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