Stop apt from installing recommended packages

The problem. Debian installs recommended packages by default, not just the packages you ask for. A single install can pull in a long chain of extras you never wanted. On my Pi 4B, installing sddm pulled in its default login theme, and that theme depends on the entire KDE Plasma workspace, which a Pi 4B cannot run.

The fix. One line in apt's config turns recommends off for the whole system:

echo 'APT::Install-Recommends "false";' > /etc/apt/apt.conf.d/99norecommends

Confirm it landed:

cat /etc/apt/apt.conf.d/99norecommends

From then on every apt install pulls only what the package truly requires. If you want a recommended package, you add it by name.