After creating a fresh installation of Ubuntu 24.04, I installed DEB Firefox from APT by following Mozilla’s instructions from here. But I noticed that it was secretly replaced with Snap Firefox. I was able to verify this by checking the About Firefox page. This is the third time I noticed this.
Well then you haven’t been following it closely. As someone else said, the reason is simple: the Snap version is more recent (like it or not) and in Ubuntu
aptis configured to take into account Snap packages.Canonical added an epoch prefix to the firefox version number. Because that epoch (1) is higher than the implicit default (0), the official ubuntu dummy package is always considered to be a higher version than the official Mozilla package. apt doesn’t look at snap packages, it installs the deb, but the ubuntu deb just runs
snap install firefoxand basically nothing else.