Mandrake was my first Linux OS.

The deb version is a pointer to the snap in their repos. Nothings being replaced, it no longer exists. The deb version of Firefox in Ubuntu repos is a wrapper that installs snap and has no binaries in it. Has been for 3 years or so.

You don’t need special docks in KDE, its all configurable through the default desktop settings. You have enough knobs to make it look like anything.