因此，根据说明，我已经添加了 ppa repo 并进行了更新。但是当我运行时：
# apt install dde
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
dde : Depends: dde-desktop but it is not going to be installed
Depends: dde-polkit-agent but it is not going to be installed
Depends: dde-dock but it is not going to be installed
Depends: dde-launcher but it is not going to be installed
Depends: dde-control-center (> 2.90.5) but it is not going to be installed
Depends: dde-daemon but it is not going to be installed
Depends: deepin-metacity but it is not going to be installed
Depends: deepin-wm but it is not going to be installed
Depends: startdde but it is not going to be installed
Depends: dde-session-ui but it is not going to be installed
Depends: deepin-notifications but it is not going to be installed
Depends: deepin-menu but it is not going to be installed
Depends: deepin-terminal but it is not going to be installed
Depends: dde-calendar but it is not going to be installed
Depends: deepin-system-monitor but it is not going to be installed
Depends: deepin-image-viewer but it is not going to be installed
Depends: deepin-screenshot but it is not going to be installed
Recommends: deepin-deb-installer but it is not going to be installed
Recommends: deepin-screen-recorder but it is not going to be installed
Recommends: deepin-voice-recorder but it is not going to be installed
Recommends: deepin-shortcut-viewer but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
有办法解决这个问题吗？
编辑：我已经尝试过 aptitude 和 synaptic 方法。Aptitude 将我的依赖项减少了大约 2 个，而 synaptic 则说我需要先修复损坏的软件包。尝试命令时sudo dpkg -l | grep ^..r没有apt-mark showhold得到任何结果。
编辑2：我也尝试了第二个重复声明的解决方案，但没有成功。