@grahammechanical-
Thanks, that's what I've been expecting, but not what I'm seeing. Perhaps I didn't install everything needed? The package I installed is called mate-desktop, installed via apt-get. It shows I have version 1.12.1-1 installed, but when logging in, I see no icon near the password field (or anywhere else).
I think you should have installed ubuntu-mate-desktop instead. No harm done, just go ahead and install it now. Only the requisite additional software will be installed.
But please run sudo apt-get update and sudo apt-get upgrade first.
See the difference:
09:59 PM ~ $ acsh mate-desktop
Package: mate-desktop
Version: 1.12.1-1
Priority: optional
Section: universe/x11
Origin: Ubuntu
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Original-Maintainer: MATE Packaging Team <pkg-mate-team@lists.alioth.debian.org>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 92.2 kB
Depends: hicolor-icon-theme, libmate-desktop-2-17 (>= 1.10.0), mate-desktop-common (= 1.12.1-1),
mate-user-guide, libc6 (>= 2.4), libglib2.0-0 (>= 2.28.0), libgtk2.0-0 (>= 2.14.0), python
Breaks: mate-desktop-gnome
Replaces: mate-desktop-gnome
Homepage: http://www.mate-desktop.org/
Task: ubuntu-mate-core, ubuntu-mate-desktop, ubuntu-mate-cloudtop
Supported: 3y
Download-Size: 23.8 kB
APT-Sources: http://archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
Description: Library with common API for various MATE modules
10:00 PM ~ $ acsh ubuntu-mate-desktop
Package: ubuntu-mate-desktop
Version: 1.154
Priority: optional
Section: universe/metapackages
Source: ubuntu-mate-meta
Origin: Ubuntu
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
Installed-Size: 15.4 kB
Depends: a11y-profile-manager-indicator, account-plugin-facebook, account-plugin-flickr,
account-plugin-google, accountsservice, acpid, alsa-base, alsa-utils, anacron, apport, apport-gtk,
apport-symptoms, apturl, at-spi2-core, atril, avahi-autoipd, avahi-discover, avahi-dnsconfd,
avahi-utils, bc, blueman, brasero, brasero-cdrkit, brltty, brltty-x11, ca-certificates, caja,
caja-gksu, caja-open-terminal, caja-sendto, caja-wallpaper, cheese, colord, compiz, compiz-core,
compiz-mate, compiz-plugins, compiz-plugins-default, crda, cups-browsed, cups-core-drivers,
cups-filters-core-drivers, cups-pk-helper, cups-ppdc, dconf-cli, dconf-editor, deja-dup,
deja-dup-backend-cloudfiles, deja-dup-backend-gvfs, deja-dup-backend-s3, deja-dup-caja, dialog,
dmz-cursor-theme, engrampa, eom, espeak, ethtool, exfat-fuse, exfat-utils, ffmpegthumbnailer,
firefox, folder-color-caja, fonts-dejavu-core, fonts-freefont-ttf, fonts-liberation, fonts-nanum,
fonts-noto, fonts-noto-cjk, fonts-noto-mono, fonts-noto-unhinted, fonts-opendyslexic,
foomatic-db-compressed-ppds, galculator, gdb, gdebi, gdisk, genisoimage, ghostscript,
ghostscript-x, gksu, gnome-disk-utility, gnome-keyring, gnome-orca, gnome-session-canberra,
gnome-system-tools, grub2-themes-ubuntu-mate, gstreamer1.0-alsa, gstreamer1.0-plugins-base,
gstreamer1.0-plugins-good, gstreamer1.0-pulseaudio, gstreamer1.0-tools, gstreamer1.0-x, gucharmap,
gufw, gvfs, gvfs-backends, gvfs-fuse, hddtemp, hexchat, hwdata, ideviceinstaller, ifuse, im-config,
indicator-application-gtk2, indicator-sound-gtk2, inputattach, inxi, iproute, iputils-arping, iso-codes,
iw, language-selector-gnome, libaacs0, libaccount-plugin-generic-oauth, libaccount-plugin-google,
libavahi-compat-libdnssd1, libbdplus0, libbluray-bdj, libbluray-bin, libbluray1, libcanberra-gtk-module,
libcanberra-gtk3-module, libcanberra-pulse, libdvdnav4, libdvdread4, libegl1-mesa-drivers,
libfile-mimeinfo-perl, libgpod-common, libimobiledevice-utils, libmtp-runtime, libnet-dbus-perl,
libnotify-bin, libp11-kit-gnome-keyring, libpam-gnome-keyring, libpaper-utils, libplist-utils,
libproxy1-plugin-gsettings, libproxy1-plugin-networkmanager, libpurple-bin, libqt5libqgtk2,
libreoffice-avmedia-backend-gstreamer, libreoffice-calc, libreoffice-gnome, libreoffice-impress,
libreoffice-ogltrans, libreoffice-pdfimport, libreoffice-style-human, libreoffice-writer,
librsvg2-common, libsasl2-modules, libtopmenu-client-gtk2-0, libtopmenu-client-gtk3-0,
libtopmenu-server-gtk2-0, libtopmenu-server-gtk3-0, libtxc-dxtn-s2tc0, libwmf0.2-7-gtk,
libx11-protocol-perl, lightdm, lightdm-gtk-greeter, lightdm-gtk-greeter-settings, marco,
mate-accessibility-profiles, mate-applet-topmenu, mate-applets, mate-desktop-environment-core,
mate-dock-applet, mate-gnome-main-menu-applet, mate-icon-theme, mate-icon-theme-faenza,
mate-indicator-applet, mate-media, mate-menu, mate-menus, mate-netbook, mate-netspeed,
mate-notification-daemon, mate-optimus, mate-polkit, mate-power-manager, mate-screensaver,
mate-sensors-applet, mate-settings-daemon, mate-system-monitor, mate-terminal, mate-themes,
mate-tweak, mate-user-guide, mate-utils, memtest86+, mobile-broadband-provider-info, modemmanager,
mozo, network-manager, network-manager-gnome, network-manager-pptp-gnome, ntp, onboard, onboard-data,
openprinting-ppds, pidgin, pidgin-libnotify, pidgin-otr, pinentry-gtk2, plank, pluma,
plymouth-theme-ubuntu-mate-logo, plymouth-theme-ubuntu-mate-text, pm-utils, ppa-purge,
printer-driver-gutenprint, printer-driver-hpcups, printer-driver-pnm2ppa, printer-driver-postscript-hp,
pulseaudio-module-bluetooth, pulseaudio-module-x11, pulseaudio-utils, python3-aptdaemon, python3-
aptdaemon.gtk3widgets, python3-aptdaemon.pkcompat, qt4-qtconfig, rfkill, rhythmbox,
rhythmbox-plugin-cdrecorder, rhythmbox-plugins, rtkit, samba-common-bin, sane-utils, seahorse,
sessioninstaller, shotwell, simple-scan, smbclient, software-properties-gtk, speech-dispatcher,
synapse, syslinux-utils, system-config-printer-gnome, system-config-printer-udev, thunderbird, tilda,
tlp, tlp-rdw, topmenu-gtk-common, topmenu-gtk2, topmenu-gtk3, toshset, transmission-gtk,
ubuntu-drivers-common, ubuntu-mate-artwork, ubuntu-mate-core, ubuntu-mate-default-settings,
ubuntu-mate-libreoffice-draw-icons, ubuntu-mate-lightdm-theme, ubuntu-mate-welcome,
ubuntu-release-upgrader-gtk, ubuntu-sounds, unity-control-center-faces, unzip, update-manager,
update-notifier, usb-creator-gtk, usb-modeswitch, usbmuxd, vbetool, vlc, vlc-plugin-notify, whoopsie,
wireless-tools, wpasupplicant, x11-utils, x11-xserver-utils, xbitmaps, xbrlapi, xcursor-themes,
xdg-user-dirs, xdg-user-dirs-gtk, xdg-utils, xkb-data, xorg, xserver-xorg, xserver-xorg-input-all,
xserver-xorg-video-all, xterm, xul-ext-calendar-timezones, xul-ext-gdata-provider, xul-ext-lightning,
xul-ext-ubufox, xzoom, yelp, zenity, zip
Recommends: acpi-support, avahi-daemon, bluez, bluez-cups, cups, cups-bsd, cups-client, cups-filters,
fonts-guru, fonts-kacst-one, fonts-khmeros-core, fonts-lao, fonts-lklug-sinhala, fonts-sil-abyssinica,
fonts-sil-padauk, fonts-takao-pgothic, fonts-thai-tlwg, fonts-tibetan-machine, fwupd, fwupdate,
fwupdate-signed, hplip, kerneloops-daemon, laptop-detect, libnss-mdns, pcmciautils,
policykit-desktop-privileges, printer-driver-brlaser, printer-driver-c2esp, printer-driver-foo2zjs,
printer-driver-min12xxw, printer-driver-ptouch, printer-driver-pxljr, printer-driver-sag-gdi,
printer-driver-splix, snapd, ttf-ancient-fonts-symbola, ttf-ubuntu-font-family
Homepage: https://launchpad.net/ubuntu-mate/
Task: ubuntu-mate-desktop
Supported: 3y
Download-Size: 3,564 B
APT-Sources: http://archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
Description: Ubuntu MATE - full desktop
10:01 PM ~ $
where acsh = apt show.
Another place to look to confirm that you need to do the above is in /usr/share/xesssions: could you post the output of ls /usr/share/xesssions? The number of .desktop files there will give you an idea of how many desktop environments choices at login are available to you.