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.