从 20.04 更新到 ubuntu 20.10 后，删除了 freecad，当我尝试重新安装 Freecad 时，我得到了
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 resolve the situation:
The following packages have unmet dependencies:
libfreecad-python3-0.18 : Depends: libboost-regex1.71.0-icu66 but it is not installable
E: Unable to correct problems, you have held broken packages.
$ apt-cache policy freecad libfreecad-python3-0.18
Installed: (none)
Candidate: 2:0.18.4+dfsg2~202007252144~ubuntu20.10.1
Version table:
2:0.18.4+dfsg2~202007252144~ubuntu20.10.1 500
500 http://ppa.launchpad.net/freecad-maintainers/freecad-stable/ubuntu groovy/main amd64 Packages
500 http://ppa.launchpad.net/freecad-maintainers/freecad-stable/ubuntu groovy/main i386 Packages
0.18.4+dfsg2-5build1 500
500 http://ca.archive.ubuntu.com/ubuntu groovy/universe amd64 Packages
500 http://ca.archive.ubuntu.com/ubuntu groovy/universe i386 Packages
libfreecad-python3-0.18:
Installed: (none)
Candidate: 2:0.18.4+dfsg2~202007252144~ubuntu20.10.1
Version table:
2:0.18.4+dfsg2~202007252144~ubuntu20.10.1 500
500 http://ppa.launchpad.net/freecad-maintainers/freecad-stable/ubuntu groovy/main amd64 Packages
0.18.4+dfsg2-5build1 500
500 http://ca.archive.ubuntu.com/ubuntu groovy/universe amd64 Packages