I’m using archive.ubuntu.com and whatever the default apt settings in Ubuntu LTS are. I feel like a ton of debian-style packaging is simply “this is the way we’ve always done it”. debmirror, for example, is hot garbage.
I remember checking their packaging howto every few years to maybe really/properly/truly understand it, but just the sheer uselessness of the text signaled each time that it's just not worth it. Just google whatever you want copy from stackoverflow, and be done with it, don't try to understand it. (Eg. if I wanted a virtual package that provides some package so I can fake that so it won't get pulled in as useless dependency for other packages.)
I would absolutely love to maintain a metapackage and some tools on a personal apt mirror that I can add to machines and update periodically. The burden/overhead of learning the ridiculously tradition-based and overcomplicated system in use has kept me from doing it for years.
It's simple to brute force a .deb (after all it's just an ar containing two tar files, on contains the control files, and that simple), but the process, the myriad of debhelpers, obscure traditions, mandatory steps (changelog update), and whatnot are not simple at all.
I would also point out that actually getting software into Debian is no fun for newcomers either. The whole mentorship process (where you use some arcane command to upload a package you built yourself to a special website, then ask someone to look at it) is wacky. The project could really improve their onboarding process, or at least make it easier for fly by contributions.
I run a bionic and focal full mirror, and even just keeping a mirror working right with debmirror is a huge complicated mess. I don’t understand why there isn’t an overhaul of the packaging tools and mirror structure to make it a lot simpler.
apt has had support for pdiff for what, two decades now?
https://debian-administration.org/article/439/Avoiding_slow_...
I am no fan of it though, dnf is just so much better in all respects.