安装步骤：
- 添加：debhttp://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu主页面
- 添加：deb-srchttp://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu主页面
- sudo apt 更新
- sudo apt-get 安装 qgis
然后出现错误：
Setting up libqgis-gui3.4.6 (3.4.6+dfsg-1~xenial1) ...
Setting up qgis-providers (3.4.6+dfsg-1~xenial1) ...
/usr/lib/qgis/crssync: symbol lookup error: /usr/lib/libgdal.so.20: undefined symbol: _ZN6kmldom15SerializePrettyB5cxx11ERKN5boost13intrusive_ptrINS_7ElementEEE
dpkg: error processing package qgis-providers (--configure):
subprocess installed post-installation script returned error exit status 127
Setting up libqgis-analysis3.4.6 (3.4.6+dfsg-1~xenial1) ...
Setting up libqgis-app3.4.6 (3.4.6+dfsg-1~xenial1) ...
Setting up libqgis-customwidgets (3.4.6+dfsg-1~xenial1) ...
Setting up libqgis-server3.4.6 (3.4.6+dfsg-1~xenial1) ...
Setting up libqgisgrass7-3.4.6 (3.4.6+dfsg-1~xenial1) ...
Setting up libqgispython3.4.6 (3.4.6+dfsg-1~xenial1) ...
Setting up python3-pyqt5.qtwebkit (5.5.1+dfsg-3ubuntu4) ...
Setting up python3-qgis-common (3.4.6+dfsg-1~xenial1) ...
Setting up python3-qgis (3.4.6+dfsg-1~xenial1) ...
Setting up libjs-leaflet (1.0.3+dfsg-1~xenial0) ...
Setting up qgis-common (3.4.6+dfsg-1~xenial1) ...
dpkg: dependency problems prevent configuration of qgis:
qgis depends on qgis-providers (= 3.4.6+dfsg-1~xenial1); however:
Package qgis-providers is not configured yet.
dpkg: error processing package qgis (--configure):
dependency problems - leaving unconfigured
Setting up qgis-plugin-grass-common (3.4.6+dfsg-1~xenial1) ...
No apport report written because the error message indicates its a followup error from a previous failure.
Setting up qgis-provider-grass (3.4.6+dfsg-1~xenial1) ...
dpkg: dependency problems prevent configuration of qgis-plugin-grass:
qgis-plugin-grass depends on qgis (= 3.4.6+dfsg-1~xenial1); however:
Package qgis is not configured yet.
dpkg: error processing package qgis-plugin-grass (--configure):
dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
Processing triggers for libc-bin (2.23-0ubuntu11) ...
Errors were encountered while processing:
qgis-providers
qgis
qgis-plugin-grass
E: Sub-process /usr/bin/dpkg returned an error code (1)
尝试了很多安装方法都没有成功，谁遇到过怎么解决，谢谢