Gnome Software忽略apt的‘kept-back’包状态导致更新显示不一致问题求助

我遇到了一个挺奇怪的问题：Gnome Software 41.5明明显示有可用更新，但用sudo apt update && sudo apt full-upgrade却找不到可更新的包，只有几个被kept-back（保留）的包。

下面是终端的完整输出：

Hit:1 http://archive.ubuntu.com/ubuntu jammy InRelease
Hit:2 http://archive.ubuntu.com/ubuntu jammy-updates InRelease
Hit:3 http://archive.ubuntu.com/ubuntu jammy-backports InRelease
Hit:4 http://archive.ubuntu.com/ubuntu jammy-security InRelease
Hit:5 https://repo.protonvpn.com/debian stable InRelease
Hit:6 https://apt.syncthing.net syncthing InRelease
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
4 packages can be upgraded. Run 'apt list --upgradable' to see them.

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
alsa-ucm-conf gnome-remote-desktop update-notifier update-notifier-common
0 upgraded, 0 newly installed, 0 to remove and 4 not upgraded.

apt-cache policy alsa-ucm-conf
alsa-ucm-conf:
  Installed: 1.2.6.3-1ubuntu1.2
  Candidate: 1.2.6.3-1ubuntu1.2
  Version table:
 *** 1.2.6.3-1ubuntu1.2 500 (phased 70%)
        500 http://archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu jammy-updates/main i386 Packages
        100 /var/lib/dpkg/status
     1.2.6.3-1ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu jammy/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu jammy/main i386 Packages

sudo snap refresh
All snaps up to date.

我已经试过几个方法，但都没解决：

• 运行dpkg --configure -a（猜测是不是之前更新过程中出了什么奇怪的故障），没用；
• 把更新下载源从本地服务器切换到主服务器（想着可能本地源还没同步更新，但Gnome Software用的是主源？），也没效果。

我的系统是Ubuntu 22.04.1 LTS，才装了一周，之前更新都很顺利，没出过异常。

想请教各位：为什么会出现这种显示不一致的情况？如果我点击Gnome Software的更新按钮，会不会和apt/dpkg的状态冲突，导致系统出问题？

备注：内容来源于stack exchange，提问作者G37H