A quick shout-out to apt-smart
"Smart, automated Debian/Ubuntu/Linux Mint mirror selection"

I recently had the pleasure of performing a release upgrade on an old Ubuntu server. The upgrade kept failing due to issues with the mirrors that were listed in /etc/apt/sources.list. Rather than resolving the issue by manually editing the sources, I stumbled across apt-smart, which auto-updated my mirror list, optimizing for speed.
Check it out here: https://github.com/martin68/apt-smart
After installing the package, I let apt-smart automatically fix my broken mirrors:
# Discover available mirrors, rank the mirrors by connection speed and
# update status and update /etc/apt/sources.list to use the best available mirror.
sudo apt-smart -a
A few minutes later I was running the release upgrade without issue.

