Ubuntu 20.04桌面登录后所有应用及背景异常变暗问题求助

各位大佬好，我遇到一个特别奇怪的问题，之前看到过“登录时屏幕亮度0%、启动时变暗”的案例，但我的情况是发生在台式机上，具体表现如下：

• 登录提示界面的屏幕亮度是正常满格的，但登录后会听到一声蜂鸣，紧接着除了鼠标光标之外，所有应用和桌面背景都变暗了
• 用VLC播放视频时，亮度会自动恢复到最大；但只要切换出VLC窗口，所有内容又会立刻变回暗的状态
• 这种亮度自动调节的行为本来应该是笔记本才有的，台式机出现这个问题实在反常
• 而且这个问题是随机出现的，有时候自己就好了，但过几天或几周又会复发

已尝试的解决方法 #

我已经试了下面这些操作，但都没解决问题：

• 禁用GNOME电源管理的环境光感应：gsettings set org.gnome.settings-daemon.plugins.power ambient-enabled false
• 修改GRUB启动参数：GRUB_CMDLINE_LINUX="acpi_osi=Linux acpi_backlight=none"
• 在Ubuntu系统和BIOS里都禁用了电源管理功能
• 用xrandr检查亮度已经是100%
• 第三方亮度控制软件Brightness Controller也调到了100%

另外说明一下：我没有独立显卡，用的是主板集成的核显。

系统及硬件信息 #

操作系统信息 #

lsb_release -a 输出：
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.5 LTS
Release:    20.04
Codename:   focal

hostnamectl 输出：
Static hostname: desktop-gigabyte
Icon name: computer-desktop
Chassis: desktop
Machine ID: 991cfb62403b4b22ab380e98f552eeb6
Boot ID: 51067401f74141c3a6e524778b013817
Operating System: Ubuntu 20.04.5 LTS
Kernel: Linux 5.13.0-44-generic
Architecture: x86-64

硬件信息 #

desktop-gigabyte
description: Desktop Computer
product: B365M DS3H (Default string)
vendor: Gigabyte Technology Co., Ltd.
version: Default string
serial: Default string
width: 64 bits
capabilities: smbios-3.1.1 dmi-3.1.1 smp vsyscall32
configuration: boot=normal chassis=desktop family=Default string sku=Default string uuid=B4022E03-9904-CA05-BE06-340700080009
*-core
description: Motherboard
product: B365M DS3H
vendor: Gigabyte Technology Co., Ltd.
physical id: 0
version: x.x
serial: Default string
slot: Default string
*-firmware
description: BIOS
vendor: American Megatrends Inc.
physical id: 0
version: F5
date: 08/13/2019
size: 64KiB
capacity: 16MiB
capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int14serial int17printer acpi usb biosbootspecification uefi
*-memory
description: System Memory
physical id: 35
slot: System board or motherboard
size: 16GiB
*-bank:0
description: [empty]
physical id: 0
slot: ChannelA-DIMM0
*-bank:1
description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2666 MHz (0.4 ns)
vendor: Fujitsu
physical id: 1
serial: 39A40400
slot: ChannelA-DIMM1
size: 16GiB
width: 64 bits
clock: 2666MHz (0.4ns)
*-bank:2
description: [empty]
physical id: 2
slot: ChannelB-DIMM0
*-bank:3
description: [empty]
physical id: 3
slot: ChannelB-DIMM1
*-cache:0
description: L1 cache
physical id: 3b
slot: L1 Cache
size: 384KiB
capacity: 384KiB
capabilities: synchronous internal write-back unified
configuration: level=1
*-cache:1
description: L2 cache
physical id: 3c
slot: L2 Cache
size: 1536KiB
capacity: 1536KiB
capabilities: synchronous internal write-back unified
configuration: level=2
*-cache:2
description: L3 cache
physical id: 3d
slot: L3 Cache
size: 9MiB
capacity: 9MiB
capabilities: synchronous internal write-back unified
configuration: level=3
*-cpu
description: CPU
product: Intel(R) Core(TM) i5-9600K CPU @ 3.70GHz
vendor: Intel Corp.
physical id: 3e
bus info: cpu@0
version: Intel(R) Core(TM) i5-9600K CPU @ 3.70GHz
serial: To Be Filled By O.E.M.
slot: U3E1
size: 4388MHz
capacity: 4600MHz
width: 64 bits
clock: 100MHz
capabilities: lm fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp x86-64 constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault invpcid_single ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp md_clear flush_l1d arch_capabilities cpufreq
configuration: cores=6 enabledcores=6 threads=6
*-pci
description: Host bridge
product: 8th Gen Core Processor Host Bridge/DRAM Registers
vendor: Intel Corporation
physical id: 100
bus info: pci@0000:00:00.0
version: 0a
width: 32 bits
clock: 33MHz
configuration: driver=skl_uncore
resources: irq:0
*-display
description: VGA compatible controller
product: UHD Graphics 630 (Desktop 9 Series)
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
resources: irq:136 memory:f6000000-f6ffffff memory:e0000000-efffffff ioport:f000(size=64) memory:c0000-dffff
*-generic UNCLAIMED
description: System peripheral
product: Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th/8th Gen Core Processor Gaussian Mixture Model
vendor: Intel Corporation
physical id: 8
bus info: pci@0000:00:08.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: msi pm bus_master cap_list
configuration: latency=0
resources: memory:f722e000-f722efff
*-usb
description: USB controller
product: 200 Series/Z370 Chipset Family USB 3.0 xHCI Controller
vendor: Intel Corporation
physical id: 14
bus info: pci@0000:00:14.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm msi xhci bus_master cap_list
configuration: driver=xhci_hcd latency=0
resources: irq:132 memory:f7210000-f721ffff
*-usbhost:0
product: xHCI Host Controller
vendor: Linux 5.13.0-44-generic xhci-hcd
physical id: 0
bus info: usb@1
logical name: usb1
version: 5.13
capabilities: usb-2.00
configuration: driver=hub slots=16 speed=480Mbit/s
*-usb:0
description: Mouse
product: USB OPTICAL MOUSE
vendor: [Maxxter]
physical id: 1
bus info: usb@1:1
version: 1.00
capabilities: usb-1.10
configuration: driver=usbhid maxpower=100mA speed=2Mbit/s
*-usb:1
description: Mouse
vendor: Racal Data Group
physical id: 2
bus info: usb@1:2
version: 0.01
capabilities: usb-1.10
configuration: driver=usbhid maxpower=202mA speed=12Mbit/s
*-usb:2
description: Bluetooth wireless interface
product: CSR8510 A10
vendor: Cambridge Silicon Radio, Ltd
physical id: 5
bus info: usb@1:5
version: 88.91
capabilities: bluetooth usb-2.00
configuration: driver=btusb maxpower=100mA speed=12Mbit/s
*-usb:3
description: Keyboard
product: USB NetVista Full Width Keyboard.
vendor: LITE-ON Technology
physical id: 8
bus info: usb@1:8
version: 1.09
capabilities: usb-1.10
configuration: driver=usbhid maxpower=70mA speed=2Mbit/s
*-usbhost:1
product: xHCI Host Controller
vendor: Linux 5.13.0-44-generic xhci-hcd
physical id: 1
bus info: usb@2
logical name: usb2
version: 5.13
capabilities: usb-3.00
configuration: driver=hub slots=8 speed=5000Mbit/s
*-communication
description: Communication controller
product: 200 Series PCH CSME HECI #1
vendor: Intel Corporation
physical id: 16
bus info: pci@0000:00:16.0
version: 00
width: 64 bits
clock: 33MHz
capabilities: pm msi bus_master cap_list
configuration: driver=mei_me latency=0
resources: irq:135 memory:f722d000-f722dfff
*-sata
description: SATA controller
product: 200 Series PCH SATA controller [AHCI mode]
vendor: Intel Corporation
physical id: 17
bus info: pci@0000:00:17.0
version: 00
width: 32 bits
clock: 66MHz
capabilities: sata msi pm ahci_1.0 bus_master cap_list
configuration: driver=ahci latency=0
resources: irq:134 memory:f7228000-f7229fff memory:f722c000-f722c0ff ioport:f090(size=8) ioport:f080(size=4) ioport:f060(size=32) memory:f722b000-f722b7ff
*-pci:0
description: PCI bridge
product: 200 Series PCH PCI Express Root Port #19
vendor: Intel Corporation
physical id: 1b
bus info: pci@0000:00:1b.0
version: f0
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:122
*-pci:1
description: PCI bridge
product: 200 Series PCH PCI Express Root Port #20
vendor: Intel Corporation
physical id: 1b.3
bus info: pci@0000:00:1b.3
version: f0
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:123
*-pci:2
description: PCI bridge
product: 200 Series PCH PCI Express Root Port #21
vendor: Intel Corporation
physical id: 1b.4
bus info: pci@0000:00:1b.4
version: f0
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:124
*-pci:3
description: PCI bridge
product: 200 Series PCH PCI Express Root Port #3
vendor: Intel Corporation
physical id: 1c
bus info: pci@0000:00:1c.0
version: f0
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:125
*-pci:4
description: PCI bridge
product: 200 Series PCH PCI Express Root Port #4
vendor: Intel Corporation
physical id: 1c.3
bus info: pci@0000:00:1c.3
version: f0
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:126
*-pci:5
description: PCI bridge
product: 200 Series PCH PCI Express Root Port #5
vendor: Intel Corporation
physical id: 1c.4
bus info: pci@0000:00:1c.4
version: f0
width: 32 bits
clock: 33MHz
capabilities: pci pciexpress msi pm normal_decode bus_master cap_list
configuration: driver=pcieport
resources: irq:127 ioport:e000(size=4096) memory:f7100000-f71fffff
*-network
description: Ethernet interface
product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:06:00.0
logical name: enp6s0
version: 16
serial: b4:2e:99:ca:be:34
size: 100Mbit/s
capacity: 1Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=r8168 driverversion=8.048.00-NAPI duplex=full ip=192.168.0.113 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s
resources: irq:133 ioport:e000(size=256) memory:f7104000-f7104fff memory:f7100000-f7103fff
*-pci:6
description: PCI bridge
product: 200 Series PCH PCI Express Root Port #6
vendor: Intel Corporation
physical id: 1