Setting the Default Desktop Environment in Ubuntu 20.04

I have upgraded my Ubuntu 16.04 to 20.04 and have installed Xfce which I'd like to set as the default DE when logging into my system. However, everytime I login with Xfce and logout, Ubuntu forgets Xfce as the default DE and goes back to the option Ubuntu (Unity).

Following How do I set the default desktop environment on 18.04 (Bionic)?

I tried

sudo update-alternatives --config x-session-manager

in the terminal. However, what I get is

There are 3 choices for the alternative x-session-manager (providing /usr/bin/x-session-manager).


  Selection    Path                    Priority   Status
------------------------------------------------------------
  0            /usr/bin/gnome-session   50        auto mode
  1            /usr/bin/gnome-session   50        manual mode
  2            /usr/bin/startxfce4      50        manual mode
* 3            /usr/bin/xfce4-session   40        manual mode

Press <enter> to keep the current choice[*], or type selection number: 

which apparently indicates that Xfce should be the default DE which is not the case. Any help would be appreciated.