Firefox stable vs Firefox ESR super stable

[Moltke]

i don't know what you mean:

Code:

sudo mv firefox-esr /opt

I mean my own:

Code:

sudo apt autoremove --purge firefox

Code:

sudo add-apt-repository ppa:mozillateam/ppa

Code:

sudo apt-get update

Code:

sudo apt install firefox-esr

Firefox regular stable has been uninstalled. Firefox ESR stable has been installed. Am I correct? I don't like to keep it both

Yes, looks like it. Is Firefox still around in your system? If it's not, then you did remove it. My first statement, "I don't know what you mean", was about the term "super stable" you used. I use Firefox beta, and for me, it works well; no bugs or issues whatsoever. At some point I even used FF developer edition, but that one was quite buggy.