I was using Linux Mint Cinnamon before my laptop computer crashed. When I started reinstalling everything, I decided to go with Linux Mint Xfce. Instead of reinstalling Google Chrome, I opted to install Chromium. Chrome is based on it. Recently, I decided to switch to Vivaldi, which is also based on Chromium.
Xfce is a desktop environment, just like Cinnamon. The problem I had with Cinnamon was that I had to restart it after a few hours (with control-alt-escape) because it consumed more and more memory as the hours passed. The same thing went for Nemo, the file manager. I just had to close that one to get the memory back.
I use Gmail as my e-mail provider. I download the messages into Mozilla Thunderbird, which I back up daily to Dropbox. After I installed Chromium and set it as my default web browser, the links in messages within Thunderbird still brought up Firefox when I clicked on them.
After I switched to Vivaldi, I clicked on the Dropbox icon and then the “Launch Dropbox Website” link. It brought up Firefox.
Within Thunderbird, I had to go to Preferences > Attachments > Incoming to set the default web browser for attachments, for both http and https, to Vivaldi.
In Linux Mint Xfce, I had to go to the menu item, “Preferred Applications”, to manually set the preferred web browser to Vivaldi (at /usr/bin/vivaldi-stable).
To fix the problem with the Dropbox icon, I had to bring up the Linux Mint Xfce “Mime Type Editor”. I changed every instance of Firefox to Vivaldi in the “Default Application” column.
I could find nothing else bringing up Firefox, which told me it was safe to uninstall it, which is what I did next.