1.按照官网的流程输入命令https://qgis.org/en/site/forusers/alldownloads.html#debian-ubuntu
出现
1 (base) server123@ubuntu:~$ sudo apt-get install qgis 2 Reading package lists... Done 3 Building dependency tree 4 Reading state information... Done 5 Some packages could not be installed. This may mean that you have 6 requested an impossible situation or if you are using the unstable 7 distribution that some required packages have not yet been created 8 or been moved out of Incoming. 9 The following information may help to resolve the situation: 10 11 The following packages have unmet dependencies: 12 qgis : Depends: libgdal20 (>= 1.8.0) but it is not going to be installed 13 Depends: libqgis-3d3.16.3 but it is not going to be installed 14 Depends: libqgis-analysis3.16.3 but it is not going to be installed 15 Depends: libqgis-app3.16.3 but it is not going to be installed 16 Depends: libqgis-core3.16.3 but it is not going to be installed 17 Depends: libqgis-gui3.16.3 but it is not going to be installed 18 Depends: python3-qgis (= 1:3.16.3+28bionic) but it is not going to be installed 19 Depends: qgis-providers (= 1:3.16.3+28bionic) but it is not going to be installed 20 Recommends: qgis-plugin-grass but it is not going to be installed 21 E: Unable to correct problems, you have held broken packages.
2.在网上试了很多办法都不行，崩溃
3.看到https://qastack.cn/gis/217727/broken-packages-and-unmet-dependency-installation-qgis-postgresql-and-postgis-u
使用
1 sudo aptitude install qgis python-qgis qgis-plugin-grass
先选no，再选yes，成功！