Keep at least 10% of drive space to avoid:

• SSD wear
• HDD fragmentation

Determine free space on Linux / macOS / Windows Subsystem for Linux with “ncdu”. ncdu uses Ncurses terminal graphics to quickly show the biggest files in the Linux filesystem tree. ncdu is very handy to find large files or directories that may be unneeded.

df -h

gives a drive-level summary of disk usage.

Package managers cache installed files in case of need to reinstall, but the packages can be redownloaded if needed to save disk space by clearing the cache. Clear the package cache–for APT (common in Debian-based systems):

apt autoclean

or for DNF (Fedora, RHEL, CentOS):

dnf clean dbcache

Remove unwanted packages

TeX Live documentation can consume a lot of disk space. To cleanup the documentation, consider removing packages matching texlive-*doc. This also removes texlive-full but with no detriment to TeX Live working.

Related:

• Find largest directory
• Clean Pacman unused packages