I'm using Enlightenment WM as a DE, instead of Mate since a couple of weeks. I encountered some issues when trying to make it my daily. Here are my tips for those who wants to do the same.

Lack of system tray

The deskbar provided by E contains a module for the system tray, however it doesn't support the old Xembed protocol anymore. The one that's used by Update Station and NetworkMgr.
The only fix this that I found is not very elegant, but it works.

Install stalonetray sudo pkg install stalonetray

Create a configuration file for stalonetray as ~/.stalonetrayrc

geometry 1x1-0+0
parent_bg false
background "#202020"
grow_gravity NE
icon_gravity NE
icon_size 24
sticky true
window_layer bottom
kludges force_icons_size
window_type desktop

You can set the background the color you want. There is a way to make the background transparent (set parent_bg to true), but in E is not working correctly.

Create a .desktop file as ~/.local/share/applications/StaloneTray.desktop

[Desktop Entry]
Hidden=false
Exec=bash -c 'sleep 5; stalonetray'
Icon=systemtray
Type=Application
NoDisplay=false
Version=1.0
StartupNotify=false
StartupWMClass=
Comment=
DBusActivatable=false
Categories=System;
Terminal=false
Name=StaloneTray
GenericName=Tray Area

Note the sleep command inside Exec. It's needed to make it render the icons properly. If it launches too early, the icons would be blank.

Set the application to start at login.
1. Go to Enlightenment Settings, then Apps, then Startup Applications.
2. Go to the Applications tab, then search for StaloneTray and click the + Add button.

Starting Update station and NetworkMgr

Go to Enlightenment Settings, then Apps, then Startup Applications.
Go to the System tab, then search for Update Station and NetworkMgr and click the + Add button.

"E" application quirks and crashes

There are some applications specifically made for E, and build with its EFL libraries. Unfortunately, most of them are not working correctly. At least here in FreeBSD.

ecrire (Text Editor): it crashes randomly
ephoto (Photo manager like Shotwell): seems to work fine
evisum (Task manager and system monitor): works fine
rage (Video Player): it starts lots of threads trying to create thumbnails for your videos, impacting heavily on the system load. Even though it should stop when all thumbnails are generated, I prefer to not use it
terminology (Terminal emulator): it works fine, but out of the box ls and other commands doesnt seems to show colors. There is a workaround:

Workaround for colored "ls" in terminology

Go to Elightenment Settings and search for Advanced, then Environment Variables
Add the variable COLORTERM and set it to truecolor

Consistent theme with GTK and QT applications

Icons

This is for both GTK and QT applications.

Download the e-gtk-pro-paprirus.tar.xz icon package from here: https://www.pling.com/p/1909560
Install it in ~/.local/share/icons
Go to Enlightenment Settings, then Look, the Applications Theme
Icons tab, then search for e-gtk-pro-papirus icons and Apply them

GTK applications

Download the e-gtk-pro.tar.xz theme package from here: https://www.pling.com/p/1909560
Install it in ~/.themes
Go to Enlightenment Settings, then Look, the Applications Theme
GTK Applications tab, then search for e-gtk-pro icons and Apply it

Consistent theme for 'Update Station', 'NetworkMgr' and 'Software Station'

These applications are launched as user root, so you need to copy the same theme also into the /root/.themes directory.

sudo -i
mkdir /root/.themes
cp -r /home/YOUR_USER/.themes/e-gtk-pro /root/.themes/

QT5 and applications

Install qt5ct, qt5-style-plugins, gtk-murrine-engine, gnome-themes-extra

sudo pkg install qt5ct qt5-style-plugins gtk-murrine-engine gnome-themes-extra

Go to Elightenment Settings and search for Advanced, then Environment Variables
Add the variable QT_QPA_PLATFORMTHEME and set it to qt5ct
Add the variable QT_STYLE_OVERRIDE as UNSET
Open qt5ct, then:
1. Set the style to gtk2
2. Set the fonts to Noto Sans 10 and Noto Sans Mono 10
3. Set the icon theme to e-gtk-pro-papirus
4. Set the window buttons to have no icons

QT6 applications

Unfortunately, there is no qt6-style-plugin package to make it use the gtk2 theme, so we must use Kvantum and the most similar kvanum theme available... Unfortunately 2: there is no kvantum engine for QT5, to be able to use the same kvantum styles in both QT5 and QT6.

Install qt6ct, Kvantum

sudo pkg install qt6ct, Kvantum

Go to Elightenment Settings and search for Advanced, then Environment Variables
Add the variable QT_QPA_PLATFORMTHEME and set it to qt6ct even if you set it previously as qt5ct. It will work for both.
Add the variable QT_STYLE_OVERRIDE as UNSET
Open kvantummanager, then
1. Go to Change/Remove Theme and set the theme to KvFlat. It's not identical to the default E theme, but close enough.
Open qt6ct, then
1. Set the style to kvantum
2. Set the fonts to Noto Sans 10 and Noto Sans Mono 10
3. Set the icon theme to e-gtk-pro-papirus
4. Set the window buttons to have no icons

Cursor

Here we want to keep the cool animated Enlightenment cursor, while using in other applications a clone of it. However, some applications would use the default Xorg cursors. With this steps we are setting this clone of the default E cursor to all applications.

Download the E-2024 cursor theme: https://www.enlightenment-themes.org/p/2064022
Install it in ~/.local/share/icons
Go to Elightenment Settings and search for Advanced, then Environment Variables
Add the variable XCURSOR_PATH and set it to /home/YOUR_USER/.icons:/home/YOUR_USER/.local/share/icons:/usr/local/share/icons (change YOUR_USER with your username 😉 )
Add the variable XCURSOR_THEME and set it to E-2024
Add the variable XCURSOR_SIZE and set it to 34 (unfortunately, it's off by 1 pixel when compared to the E cursor, but there's no way to make it perfect).

Note that the cursor size might be different on scale factors different from 1.2, which is the one that I'm using. You'll have to adjust it.

Icons disappearing on start

That one is tricky... There seems to be some kind of timing issues between enlightenment start and its icon cache daemon efreetd. I haven;t found a perfect solution yet, but only this klunky workaround.

Create a desktop file named ~/.local/share/applications/RestartEfreetd.desktop

[Desktop Entry]
Hidden=false
Exec=bash -c 'sleep 8; killall -5 efreetd'
Icon=enlightenment
Type=Application
NoDisplay=false
Version=1.0
StartupNotify=false
StartupWMClass=
Comment=
DBusActivatable=false
Categories=System;
Terminal=false
Name=Restart Efreetd
GenericName=Restarts Enlightenment cache daemon

Note that the 8 seconds of sleep might be tuned.

Set the application to start at login.
1. Go to Enlightenment Settings, then Apps, then Startup Applications.
2. Go to the Applications tab, then search for Restart Efreetd and click the + Add button.

What will happens is that:

enlightenment starts (it could be with or without blank icons)
after 8 seconds efreetd restarts then enlightenment should refresh the icons

Other workarounds would be to killall -5 efreetd manually, or restart Enlightenment on the fly by choosing in the Enlightenment desktop menu: Enligtenment -> Restart

Conclusions

With this steps you should be able to run Enlightenment alongsine Mate and use all GhostBSD default apps maintaining the same style.

There are some applications which I prefer to the default ones:

leafpad instead of pluma
audacious-qt5 and easytag instead of rhythmbox
mpv instead of vlc (anyway, vlc is excellent and will look good too)