How to completely separate desktop enviroments?
How could I completely separate desktop environments from each other? For example if I install Cinnamon and MATE, both desktop environments' applications show in the main menu, and the launchers list them too, even if they are useless in the actual DE. So in the end everything just messes up when there are more than one DE installed.
Is there any method to separate them more?
You can do it the «hard way».
1.- Open your DE. For instance, Cinnamon.
2.- Check every installed application in the menu and write down those you don't want to appear.
3.- Open your File Manager (Nautilus or Nemo)
4.- Go to /usr/share/applications (also check .local/share/applications in your home folder) and identify the file name of the applications you don't want to appear under your present DE
5.- Open a terminal and type
cd /usr/share/applications
6.- For each application, type
sudo nano [nameoftheprogram].desktop
For instance:
sudo nano yelp.desktop
7.- Find this line
OnlyShowIn=
and delete the DE you don't want. If there isn't this line, add it and add also the DE.
8.- Repeat steps 6, 7 and 8 for each program.
N.B. This how-to will only help you with the mixing of programs in the menu.
No, there isn't any practical way of separating these desktop environments, but why would you want to do that anyway? Deleting a DE would remove all the contents, for example I recently installed KDE Plasma Workspace and didn't like it (screwed up my system), to find my GNOME was full of KDE deafult apps. It's hard enough to remove the whole DE, but if you manage to remove it all, that's the only to remove it.
One idea is to dual boot two copies of Linux: one set-up to use one desktop environment, and the other set-up to use another.
By dual-booting, you mostly isolate the systems. They could even be different operating systems. For example, you could install Lubuntu and Linux Mint.
If you keep /home in a separate partition, you can access this partition from both systems, whether or not you choose to share it.