sudo apt-get install dolphin
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  baloo-kf5 fonts-lato kdelibs5-data kinit kio kpackagelauncherqml
  kpackagetool5 libattica0.4 libdlrestrictions1 libdolphinvcs5 libkdecore5
  libkdeui5 libkf5baloowidgets-bin libkf5baloowidgets5 libkf5declarative-data
  libkf5declarative5 libkf5kcmutils-data libkf5kcmutils5 libkf5kiontlm5
  libkf5newstuff-data libkf5newstuff5 libkf5package-data libkf5package5
  libkf5quickaddons5 libkio5 libkonq-common libkonq5-templates libphonon4
  libqt4-svg libruby2.3 libsolid4 libstreamanalyzer0v5 libstreams0v5 phonon
  phonon-backend-gstreamer phonon-backend-gstreamer-common rake ruby
  ruby-did-you-mean ruby-minitest ruby-net-telnet ruby-power-assert
  ruby-test-unit ruby2.3 rubygems-integration
Suggested packages:
  dolphin-plugins hspell kdelibs5-plugins phonon-backend-mplayer
  phonon-backend-vlc phonon4qt5-backend-gstreamer ri ruby-dev bundler
The following NEW packages will be installed:
  baloo-kf5 dolphin fonts-lato kdelibs5-data kinit kio kpackagelauncherqml
  kpackagetool5 libattica0.4 libdlrestrictions1 libdolphinvcs5 libkdecore5
  libkdeui5 libkf5baloowidgets-bin libkf5baloowidgets5 libkf5declarative-data
  libkf5declarative5 libkf5kcmutils-data libkf5kcmutils5 libkf5kiontlm5
  libkf5newstuff-data libkf5newstuff5 libkf5package-data libkf5package5
  libkf5quickaddons5 libkio5 libkonq-common libkonq5-templates libphonon4
  libqt4-svg libruby2.3 libsolid4 libstreamanalyzer0v5 libstreams0v5 phonon
  phonon-backend-gstreamer phonon-backend-gstreamer-common rake ruby
  ruby-did-you-mean ruby-minitest ruby-net-telnet ruby-power-assert
  ruby-test-unit ruby2.3 rubygems-integration
0 upgraded, 46 newly installed, 0 to remove and 0 not upgraded.
Need to get 2,998 kB/17.6 MB of archives.
After this operation, 80.6 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Err:1 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 libruby2.3 amd64 2.3.1-2~16.04
  404  Not Found [IP: 91.189.91.26 80]
Err:2 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 ruby2.3 amd64 2.3.1-2~16.04
  404  Not Found [IP: 91.189.91.26 80]
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/r/ruby2.3/libruby2.3_2.3.1-2~16.04_amd64.deb  404  Not Found [IP: 91.189.91.26 80]

E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/r/ruby2.3/ruby2.3_2.3.1-2~16.04_amd64.deb  404  Not Found [IP: 91.189.91.26 80]

E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?