# while [ -e /snap/snapd ] ; do ls -1 /snap | xargs -L1 snap remove ; done ; apt remove snapd snap -y ; apt purge snapd snap --purge -y ; sudo apt update ; systemctl disable snapd.* ; apt-mark hold snapd snap
ワンライナー(1行コマンドとして書いたもの)で。ここを参考にして書いた。$ sudo install -d -m 0755 /etc/apt/keyrings ; wget -q https://packages.mozilla.org/apt/repo-signing-key.gpg -O- | sudo tee /etc/apt/keyrings/packages.mozilla.org.asc ; echo -e "Types: deb\nURIs: https://packages.mozilla.org/apt\nSuites: mozilla\nComponents: main\nSigned-By: /etc/apt/keyrings/packages.mozilla.org.asc" | sudo tee /etc/apt/sources.list.d/mozilla.sources ; echo -e "Package: *\nPin: origin packages.mozilla.org\nPin-Priority: 1000\n" | sudo tee /etc/apt/preferences.d/mozilla ; sudo apt update && sudo apt install firefox firefox-l10n-ja