I'd recommend a slightly differently approach. First of, remove snap all-together. Continue removing snap packages until there are none left.

    sudo snap remove firefox
    sudo snap remove gnome-3-38-2004
    sudo snap remove gtk-common-themes
    sudo snap remove core20
    sudo snap remove bare
    sudo snap remove snapd

Remove snap completely:

    sudo apt purge snapd

Then instead of adding the ppa, use flatpak with flathub (https://flatpak.org/setup/Ubuntu)