apt is Debian/Ubuntu’s package manager, wrapping dpkg with dependency resolution and repository handling.
Skip Waiting on Phased Updates
Ubuntu staggers some updates to a subset of machines first (“phased updates”), so apt upgrade can silently skip a package until your machine is picked. Setting APT::Get::Always-Include-Phased-Updates to true forces apt to include them immediately instead of waiting.
Finding the Fastest Mirror
netselect-apt benchmarks Debian mirrors by latency/throughput and writes a ready-to-use sources.list for the fastest ones. Run it with your release codename (e.g. trixie); by default it writes to ./sources.list in the current directory, so review it before copying it into /etc/apt/sources.list.
By default the generated file only enables main and contrib — pass -n/--nonfree to also include non-free. The man page only documents -n as adding non-free, but on trixie it also brings in non-free-firmware, so a plain -n run is enough to preserve both if your existing sources.list had them.
Cheatsheet
Skip Waiting on Phased Updates
sudo apt -o APT::Get::Always-Include-Phased-Updates=true upgradeFind and Use the Fastest Mirror
sudo apt install netselect-apt
sudo netselect-apt -n <release-codename> # -n also enables non-free
sudo cp sources.list /etc/apt/sources.list
sudo apt update