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.
I’m reasonably happy with XFCE/Xubuntu - it’s not as slick of a desktop as KDE or Gnome, and in some ways that’s a great thing.