Is there more technical information than this article provides? Did Firefox not have a .deb package until now? It's been a few years since I used Ubuntu, but I find that really surprising. I'm not sure what this new package is or how it differs.
* In the ancient past, when dinosaurs roamed the earth, Ubuntu distributed Firefox as a .deb
* Recently (well, in the last 2-4 years) to boost the uptake of Canonical's "snap" packaging system, Ubuntu switched to only distributing Firefox as a snap.
* There are a lot of snap haters around. Not least because canonical fucked up the update mechanism in the first year or two, had a bunch of performance problems (now mostly solved?), and made a bunch of weird broken snaps for things like docker.
* An unofficial firefox package for Ubuntu was then created, so people who didn't want to use the snap could avoid doing so.
* By some accounts, Mozilla is keen on controlling the entire release channel, so security updates don't have to wait on volunteer maintainers. (IDK if this is true or not, but I've heard second-hand claims)
* This new package lets Mozilla release to users directly, and lets snap haters avoid snap without using unofficial packages.
Yeah the Snap package is still annoying. Like every day it pops up and tells me to close Firefox to update it. So I close it, and then nothing happens. Then I wait, and nothing happens. Occasionally, it notices that I closed Firefox and applies the update. But it's a frustrating annoyance.
Depending on your distro, the Firefox package you see in the official repo is ... well packaged by the repo maintianers and some distros will include customizations like adding in bookmarks to the distro's welcome/docs/pages/etc. Sometimes even more things like feature settings are changed. It is usually not anything major and usually things that you might prefer like disabling pocket, etc.
What Mozilla is calling out here is a seperate, Mozilla-direct repo. This means you skip the official repos.
Everyone should think carefully about what this means.