Sharing the experience of using Pi4 as a desktop for moderate programmatic/casual browsing workload. Installation and setup of Mate [3] went without any hiccups. The overall response of the system was for most part comparable to couple of years old laptop (there was little bit of additional lag when opening an application). Some applications like Calibre, Ionide, Brave, Nyxt didn't work either to due graphics/UI configuration or dependency on x86 bits.
In the end, there was mainly two main stumbling blocks for PI being a desktop: 1) dragging windows around was clumsy and would leave a trail of dark unrefreshed dark border and 2) firefox was slow enough to the point of being mildly annoying. To fix latter,I started hunting around for an alternative lightweight browser. This turned out to be fruitful endeavour: From [2], I figured that part of the reason for slowish UI response was that the system may not have been using the Pi GPU (called Mali) due to lack of driver. Once I fixed that, both UI and Firefox became bit more nimble. After unsuccessfully trying out alternative browsers, Brave, Nyxt, eww, I came across qutebrowser which was truly a game changer. This browser blocks many tracking stuff on the page due to which it was not just fast but clearly outperformed all browser hardware combo I have used in the past.
The next big usage improvement came by switching from gnome to xfce4+i3. This is bit tricky to install (see [1]). But works smoothly and obliviated the need for dragging windows around the screen. All in all, turning on gpu and using qutebrowser and xfce+i3, the experience of desktop on pi surpassed that of linux or mac on more high end and mainstream hardware.
[1] https://cdaringe.com/i3-xfce
[2] https://www.dedoimedo.com/computers/rpi4-ubuntu-mate-hw-video-acceleration.html
[3] https://ubuntu-mate.org/ports/raspberry-pi/
On pi4, booting OS from USB is desirable since microSD turns out be a tad slow. The best choice of OS to run from USB is ubuntu 20.10. In my experience, its the least problematic 64bit OS to install and run from external USB.
I found xfce4+i3 to be most usable/least annoying desktop frontend. Its reasonably lean to run smoothly on pi4. The instructions for installation are here and here. The command below lists all the package required for the xfce4+i3 setup.
apt install xubuntu-desktop i3 xcb-proto libxcb1-dev libglib2.0-dev gobject-introspection libjson-glib-dev gtk-doc-tools autoconf libtool libgtk2.0-dev libxfce4ui-2-dev libxfce4util-dev xfce4-panel-dev xfce4-dev-tools libxfce4ui-1-dev libxcb1-dev libxcb-keysyms1-dev libpango1.0-dev libxcb-util0-dev libxcb-icccm4-dev libyajl-dev libstartup-notification0-dev libxcb-randr0-dev libev-dev libxcb-cursor-dev libxcb-xinerama0-dev libxcb-xkb-dev libxkbcommon-dev libxkbcommon-x11-dev autoconf xutils-dev libtool libxcb-shape0-dev libxcb-xrm-dev
pkg install x11-repo (multiple times)
pkg in tigervnc i3 aterm
export DISPLAY=:1
vncserver :1
1. edit ~/.vnc/xstartup
2. change twm --> i3-wm
3. killall Xvnc
4. vncserver :1
install and connect to 127.0.0.1:1 The final view is not great
apt install i3 i3-blocks
i3-gaps tbd
from (https://askubuntu.com/questions/874850/16-10-lightdm-failed-to-start-session-with-i3) in file /etc/lightdm/lightdm.conf change user-session key value to i3. This forces lightdm to show options for various windowmanagers