Ubuntu – XRDP fails to run on Ubuntu 17.10

I'm trying to run XRDP on an Ubuntu 17.10 server. I've done this before on an Ubuntu 16.04 desktop which was very easy, but now things fail unexpectedly now. (And they failed on a Ubuntu 17.10 desktop with a perfectly running graphical user interface on another machine.)

What I've done so far:
* I installed mate-desktop as well as xfce4 to possibly use them as window managers.
* I installed xrdp.

The service is started automatically. xrdp runs as I can connect to the service via RDP from another machine by using the remote desktop viewer provided in Ubuntu 17.10. I can enter my user name and password and confirm login. Then nothing happens for a bit of time. After that I get an error message stating the following text:

• connecting to sesman ip 127.0.0.1 port 3350
• sesman connect ok
• sending login info to session manager, please wait...
• login successful for display 10
• started connecting
• connection problem, giving up
• some problem

Well, I thought, let's look into the log files. This is the content of /etc/xrdp/xrdp.log:

• [20171204-14:24:39] [DEBUG] Closed socket 12 (AF_INET6 ::ffff:192.168.10.110 port 3389)
• [20171204-14:24:39] [DEBUG] Closed socket 11 (AF_INET6 :: port 3389)
• [20171204-14:24:39] [INFO ] Using default X.509 certificate: /etc/xrdp/cert.pem
• [20171204-14:24:39] [INFO ] Using default X.509 key file: /etc/xrdp/key.pem
• [20171204-14:24:39] [DEBUG] Security layer: requested 3, selected 0
• [20171204-14:24:39] [DEBUG] xrdp_0000362c_wm_login_mode_event_00000001
• [20171204-14:24:39] [INFO ] Cannot find keymap file /etc/xrdp/km-00000000.ini`
• [20171204-14:24:39] [INFO ] Cannot find keymap file /etc/xrdp/km-00000000.ini
• [20171204-14:24:39] [INFO ] Loading keymap file /etc/xrdp/km-00000409.ini
• [20171204-14:24:39] [WARN ] local keymap file for 0x00000000 found and doesn't match built in keymap, using local keymap file
• [20171204-14:24:46] [DEBUG] xrdp_wm_log_msg: connecting to sesman ip 127.0.0.1 port 3350
• [20171204-14:24:47] [INFO ] xrdp_wm_log_msg: sesman connect ok
• [20171204-14:24:47] [DEBUG] xrdp_wm_log_msg: sending login info to session manager, please wait...
• [20171204-14:24:47] [DEBUG] return value from xrdp_mm_connect 0
• [20171204-14:24:47] [INFO ] xrdp_wm_log_msg: login successful for display 10
• [20171204-14:24:47] [DEBUG] xrdp_wm_log_msg: started connecting
• [20171204-14:24:51] [DEBUG] Closed socket 17 (AF_UNIX)
• [20171204-14:24:54] [DEBUG] Closed socket 17 (AF_UNIX)
• (repeated many, many times)
• [20171204-14:28:11] [DEBUG] Closed socket 17 (AF_UNIX)
• [20171204-14:28:14] [DEBUG] Closed socket 17 (AF_UNIX)
• [20171204-14:28:17] [DEBUG] xrdp_wm_log_msg: connection problem, giving up
• [20171204-14:28:17] [DEBUG] Closed socket 17 (AF_UNIX)
• [20171204-14:28:17] [DEBUG] xrdp_wm_log_msg: some problem
• [20171204-14:28:17] [DEBUG] xrdp_mm_module_cleanup
• [20171204-14:28:17] [DEBUG] Closed socket 16 (AF_INET6 ::1 port 33926)

The file /var/log/xrdp-sesman.log is a bit more conclusive. If presents the following error messages:

• [20171204-14:24:57] [ERROR] X server for display 10 startup timeout
• [20171204-14:24:57] [INFO ] starting xrdp-sessvc - xpid=13891 - wmpid=13890
• [20171204-14:24:57] [ERROR] X server for display 10 startup timeout
• [20171204-14:24:57] [ERROR] another Xserver might already be active on display 10 - see log
• [20171204-14:24:57] [DEBUG] aborting connection...

I guess there have been some significant changes because of wayland? Are there some packages missing? How can I get xrdp to run on Ubuntu 17.10? Any information I could find via Google was not helpful at all. It seemed to address completely different problems. Do you have some ideas how to continue here to get XRDP up and running?