Tested on: Ubuntu 24.04.2:

lsb_release -a

Output:

No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 24.04.2 LTS
Release:	24.04
Codename:	noble

Steps

List where xfce4 will be installed from:

sudo apt update
apt policy xfce4
apt policy xfce4-goodies

Get it:

sudo apt update
sudo apt install xfce4
sudo apt install xfce4-goodies 

Select lightdm on the config screen terminal pop-up.

Reboot:

sudo systemctl reboot 

At the login screen, switch to XFCE.

Get xfce4-terminal and switch to it from Gnome Terminal:

sudo apt update
sudo apt install xfce4-terminal
sudo update-alternatives --config x-terminal-emulator

Note: xfce4-terminal does come in with xfce4-goodies:

apt-cache rdepends xfce4-terminal

Output:

xfce4-terminal
Reverse Depends:
  task-xfce-desktop
  xubuntu-desktop-minimal
  xubuntu-desktop
  xfce4-goodies

Make sure we’re using X11, not Wayland:

loginctl
loginctl show-session c2 -p Type

Install xrdp:

sudo apt update
sudo apt install xrdp
sudo adduser xrdp ssl-cert
echo "xfce4-session" > ~/.xsession
sudo systemctl restart xrdp
sudo systemctl enable xrdp

Disable suspend at the kernel:

sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target

Use unmask to re-enable.

If you see in dmesg:

[13050.392304] i915 0000:00:02.0: [drm] *ERROR* Failed to probe lspcon
[13050.392308] i915 0000:00:02.0: [drm] *ERROR* LSPCON init failed on port D

Turn off DRM (Direct Rendering Manager) polling:

sudo vi /etc/default/grub

Use:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash drm_kms_helper.poll=0"
sudo update-grub

Reboot:

sudo systemctl reboot

Get the IP address of the computer for RDP connect:

ip a