LaTeX Packages
Warm Up
- Deep breath.
- Cup of tea.
- Remove the old LaTeX junk you've installed. Search for 'texlive' or 'latex' in your package manager's installed files.
- Find tlmgrin your package manager.
tlmgr
The LaTeX Package manager is known as tlmgr, and often resides in /opt/texlive/${YEAR}/bin/x86_64-linux/tlmgr.
Double-check the location:
1ls -l /opt/texlive/${YEAR}/bin/x86_64-linux/tlmgr
2ls /opt/texlive/${YEAR}/texmf-dist/scripts/texlive/tlmgr.pl 
Double-check the year.
It should not match the current year, it should match the texlive.
Problems along the Path
You can't use tlmgr unless it's in the $PATH.
Check if it is in the $PATH then if it should be in the path:
1echo $PATH
2grep texlive -r /etc/profile*
If tlmgr is where it should be, but not in the path, you can add it temporarily:
1export PATH=${PATH}:/opt/texlive/${YEAR}/bin/x86_64-linux
...or just reboot.
Usage
Search packages:
1tlmgr search --global epstopdf
Can't find what you need? Search for a specific file instead:
1tlmgr search --global --file epstopdf-base.sty
2sudo tlmgr install epstopdf-pkg
Check how many unique licences LaTeX packages use:
1tlmgr info --list --json
2jq -r '.[].cataloguedata.license' < tex.json  | sort | uniq | wc -l
Please remember: the world does not need any more licences.
Recommended Packages
 1latexmk
 2luatex
 3titletoc
 4titlesec
 5multicol
 6microtype
 7graphicx
 8fontspec
 9makeindex
10imakeidx