Replace SNAP Firefox on Ubuntu

Snap ignores your theme and selects one of the co-packed snap themes. This is one of the drawbacks of snap.

You could remove Firefox from snap with:

    sudo snap disable firefox
    snap remove --purge firefox

For Ubuntu 22.04, the empty Firefox Deb is pre-installed as a wrapper. You have to remove it via command:

sudo apt remove --autoremove firefox

On Ubuntu 22.04, you’ll have to add a ppa now:

sudo add-apt-repository ppa:mozillateam/ppa

Now you can install it as deb:

sudo apt install -t 'o=LP-PPA-mozillateam' firefox-esr

To avoid clashes during the next updates you might setup the priority in the mozillas ppa file:

sudo nano /etc/apt/preferences.d/99mozillateamppa
Below the existing lines add the following entries:

    Package: firefox*
    Pin: release o=LP-PPA-mozillateam
    Pin-Priority: 501

To block Ubuntu’s own (empty) deb add these lines as well:

    Package: firefox*
    Pin: release o=Ubuntu
    Pin-Priority: -1

This all has been explained here in detail

I removed snap altogether, because I want to have the freedom to decide about the look & feel of my desktop - uniformly ;-)