Ubuntu Server documentation — by Canonical (Ubuntu Server docs)

Practical advice on avoiding self-inflicted breakage: do not mix releases, prefer packaged drivers, avoid make install and read APT's removal lists before confirming.

Explains how to install Flatpak on Debian, add the Flathub repository and install and run sandboxed apps, with notes on security trade-offs.

A short disambiguation page that explains the difference between the APT package system and the apt command-line tool, and points to deeper pages.