xrdp "window manager exited quickly"

I'm trying to remote on to Ubuntu (21.10) from Windows 7. I read a few web pages, which suggested to install xrdp, so I did. I'm not an expert on this topic.

From Windows 7 Remote Desktop Connection, after entering the correct password, the connection closes immediately.

I followed the accepted answer to this question:

https://unix.stackexchange.com/questions/523152/xrdp-disconnects-immediately-after-connection-from-windows10-centos-to-centos7

So I commented-out:

#test -x /etc/X11/Xsession && exec /etc/X11/Xsession
#exec /bin/sh /etc/X11/Xsession

and added:

startxfce4

But it still doesn't work. This is my xrdp log:

[20211114-19:39:36] [INFO ] starting xrdp-sesman with pid 846
[20211114-19:39:36] [INFO ] listening to port 3350 on 127.0.0.1
[20211114-19:40:53] [INFO ] shutting down sesman 1
[20211114-19:42:27] [INFO ] starting xrdp-sesman with pid 3304
[20211114-19:42:27] [INFO ] listening to port 3350 on 127.0.0.1
[20211114-19:43:21] [INFO ] A connection received from ::1 port 46468
[20211114-19:43:21] [INFO ] Terminal Server Users group is disabled, allowing authentication
[20211114-19:43:21] [INFO ] ++ created session (access granted): username peter, ip ::ffff:192.168.1.93:55657 - socket: 12
[20211114-19:43:21] [INFO ] starting Xorg session...
[20211114-19:43:21] [INFO ] calling auth_start_session from pid 3320
[20211114-19:43:21] [INFO ] /usr/lib/xorg/Xorg :10 -auth .Xauthority -config xrdp/xorg.conf -noreset -nolisten tcp -logfile .xorgxrdp.%s.log  
[20211114-19:43:22] [INFO ] waiting for window manager (pid 3321) to exit
[20211114-19:43:22] [CORE ] window manager exited quickly (0 secs). Window manager config problem?
[20211114-19:43:22] [INFO ] Cleaning up session. Calling auth_stop_session and auth_end from pid 3320
[20211114-19:43:22] [INFO ] ++ terminated session:  username peter, display :10.0, session_pid 3320, ip ::ffff:192.168.1.93:55657 - socket: 12