[20201211-14:25:44] [INFO ] starting xrdp with pid 2294
[20201211-14:25:44] [INFO ] address [0.0.0.0] port [3389] mode 1
[20201211-14:25:44] [INFO ] listening to port 3389 on 0.0.0.0
[20201211-14:25:44] [INFO ] xrdp_listen_pp done
[20210104-23:13:52] [INFO ] Socket 12: AF_INET6 connection received from ::ffff:192.168.1.3 port 62282
[20210104-23:13:52] [DEBUG] Closed socket 12 (AF_INET6 ::ffff:192.168.1.2 port 3389)
[20210104-23:13:52] [DEBUG] Closed socket 11 (AF_INET6 :: port 3389)
[20210104-23:13:52] [INFO ] Using default X.509 certificate: /etc/xrdp/cert.pem
[20210104-23:13:52] [INFO ] Using default X.509 key file: /etc/xrdp/key.pem
[20210104-23:13:52] [DEBUG] TLSv1.3 enabled
[20210104-23:13:52] [DEBUG] TLSv1.2 enabled
[20210104-23:13:52] [DEBUG] Security layer: requested 11, selected 1
[20210104-23:13:52] [INFO ] connected client computer name: KAMEL-LAPTOP
[20210104-23:13:52] [INFO ] adding channel item name rdpdr chan_id 1004 flags 0x80800000
[20210104-23:13:52] [INFO ] adding channel item name rdpsnd chan_id 1005 flags 0xc0000000
[20210104-23:13:52] [INFO ] adding channel item name cliprdr chan_id 1006 flags 0xc0a00000
[20210104-23:13:52] [INFO ] adding channel item name drdynvc chan_id 1007 flags 0xc0800000
[20210104-23:13:52] [INFO ] TLS connection established from ::ffff:192.168.1.3 port 62282: TLSv1.2 with cipher ECDHE-RSA->
[20210104-23:13:52] [DEBUG] xrdp_00000a37_wm_login_mode_event_00000001
[20210104-23:13:52] [INFO ] Loading keymap file /etc/xrdp/km-0000040c.ini
[20210104-23:13:52] [WARN ] local keymap file for 0x0000040c found and doesn't match built in keymap, using local keymap >
[20210104-23:13:52] [DEBUG] xrdp_wm_log_msg: connecting to sesman ip 127.0.0.1 port 3350
[20210104-23:13:56] [DEBUG] Closed socket 18 (AF_INET6 ::1 port 48086)
[20210104-23:14:00] [DEBUG] Closed socket 18 (AF_INET6 ::1 port 48088)
[20210104-23:14:04] [DEBUG] Closed socket 18 (AF_INET6 ::1 port 48090)
[20210104-23:14:08] [ERROR] xrdp_wm_log_msg: Error connecting to sesman: 127.0.0.1 port: 3350
[20210104-23:14:08] [DEBUG] Closed socket 18 (AF_INET6 ::1 port 48092)
[20210104-23:14:08] [DEBUG] return value from xrdp_mm_connect 1
[20210104-23:14:08] [DEBUG] Closed socket 12 (AF_INET6 ::ffff:192.168.1.2 port 3389)
          
xrdp-sesman is running.
kamel@odroid-buster64:~$ sudo service xrdp status
● xrdp.service - xrdp daemon
     Loaded: loaded (/lib/systemd/system/xrdp.service; enabled; vendor preset: enabled)
     Active: active (running) since Wed 2021-01-06 08:30:28 EST; 5min ago
       Docs: man:xrdp(8)
             man:xrdp.ini(5)
    Process: 2671 ExecStartPre=/bin/sh /usr/share/xrdp/socksetup (code=exited, status=0/SUCCESS)
    Process: 2680 ExecStart=/usr/sbin/xrdp $XRDP_OPTIONS (code=exited, status=0/SUCCESS)
   Main PID: 2681 (xrdp)
      Tasks: 2 (limit: 3846)
     Memory: 15.1M
     CGroup: /system.slice/xrdp.service
             ├─2681 /usr/sbin/xrdp
             └─2689 /usr/sbin/xrdp
Jan 06 08:31:49 odroid-buster64 xrdp[2689]: (2689)(547848785936)[ERROR] xrdp_wm_log_msg: Error connecting to sesman: 127.>
Jan 06 08:31:49 odroid-buster64 xrdp[2689]: (2689)(547848785936)[DEBUG] Closed socket 18 (AF_INET6 ::1 port 49278)
Jan 06 08:31:49 odroid-buster64 xrdp[2689]: (2689)(547848785936)[DEBUG] return value from xrdp_mm_connect 1
Jan 06 08:33:10 odroid-buster64 xrdp[2689]: (2689)(547848785936)[DEBUG] xrdp_wm_log_msg: connecting to sesman ip 127.0.0.>
Jan 06 08:33:14 odroid-buster64 xrdp[2689]: (2689)(547848785936)[DEBUG] Closed socket 18 (AF_INET6 ::1 port 49280)
Jan 06 08:33:18 odroid-buster64 xrdp[2689]: (2689)(547848785936)[DEBUG] Closed socket 18 (AF_INET6 ::1 port 49282)
Jan 06 08:33:22 odroid-buster64 xrdp[2689]: (2689)(547848785936)[DEBUG] Closed socket 18 (AF_INET6 ::1 port 49284)
Jan 06 08:33:26 odroid-buster64 xrdp[2689]: (2689)(547848785936)[ERROR] xrdp_wm_log_msg: Error connecting to sesman: 127.>
Jan 06 08:33:26 odroid-buster64 xrdp[2689]: (2689)(547848785936)[DEBUG] Closed socket 18 (AF_INET6 ::1 port 49286)
Jan 06 08:33:26 odroid-buster64 xrdp[2689]: (2689)(547848785936)[DEBUG] return value from xrdp_mm_connect 1
kamel@odroid-buster64:~$ sudo service xrdp-sesman status
● xrdp-sesman.service - xrdp session manager
     Loaded: loaded (/lib/systemd/system/xrdp-sesman.service; enabled; vendor preset: enabled)
     Active: active (running) since Wed 2021-01-06 08:30:27 EST; 6min ago
       Docs: man:xrdp-sesman(8)
             man:sesman.ini(5)
    Process: 2660 ExecStart=/usr/sbin/xrdp-sesman $SESMAN_OPTIONS (code=exited, status=0/SUCCESS)
   Main PID: 2670 (xrdp-sesman)
      Tasks: 1 (limit: 3846)
     Memory: 696.0K
     CGroup: /system.slice/xrdp-sesman.service
             └─2670 /usr/sbin/xrdp-sesman
Jan 06 08:30:27 odroid-buster64 systemd[1]: Starting xrdp session manager...
Jan 06 08:30:27 odroid-buster64 xrdp-sesman[2660]: (2660)(547969943856)[DEBUG] libscp initialized
Jan 06 08:30:27 odroid-buster64 xrdp-sesman[2660]: (2660)(547969943856)[DEBUG] Testing if xrdp-sesman can listen on 127.0>
Jan 06 08:30:27 odroid-buster64 xrdp-sesman[2660]: (2660)(547969943856)[DEBUG] Closed socket 5 (AF_INET6 ::1 port 3350)
Jan 06 08:30:27 odroid-buster64 xrdp-sesman[2670]: (2670)(547969943856)[INFO ] starting xrdp-sesman with pid 2670
Jan 06 08:30:27 odroid-buster64 systemd[1]: Started xrdp session manager.
Jan 06 08:30:27 odroid-buster64 xrdp-sesman[2670]: (2670)(547969943856)[INFO ] listening to port 3350 on 127.0.0.1
          
Thanks for that.
xrdp and xrdp-sesman use TCP port 3350 on the loopback interface (127.0.0.1) to communicate. From above it looks like xrdp-sesman is listening on 3350, but xrdp is for some reason unable to connect to it.
Firstly; are you running a firewall on the loopback interface? If so, could you temporarily disable it and see if that makes a difference?
If that's not it, can you please install nmap if it's not installed (sudo apt install nmap), and then run the following commands which I'll need the output for. The first command checks the processes are using the same network stack, the second looks for processes listening on port 3350, and the third probes port 3350 to see if it's open.
sudo ps -e -o pid,netns,command | grep xrdp
sudo ss -alp 'sport = 3350'
sudo nmap -p 3350 127.0.0.1
          
My problem "Error connecting to sesman: 127.0.0.1 port: 3350" on xrdp after upgrade to Ubuntu 23.10 mantic was fixed by disabling ipv6 on all interfaces.
I had ipv6 enabled only on some interfaces, probably this made xrdp to attempt connecting to xrdp-sesman via ipv6, while the loopback interface had ipv6 disabled. Interestingly, the problem appeared after upgrade to Ubuntu 23.10 mantic without changing any config.
This is only the last piece I tried that solved the xRDP connection, not sure if it was the only one needed.

Before this, I also migrated from Wayland to Xorg and from gnome to xfce, not sure if those were actually needed.
How to disable ipv6 on all interfaces:
sysctl -a | grep disable_ipv6
net.ipv6.conf.all.disable_ipv6 = 1

net.ipv6.conf.default.disable_ipv6 = 1

net.ipv6.conf.enp89s0.disable_ipv6 = 1

net.ipv6.conf.lo.disable_ipv6 = 1

net.ipv6.conf.wlo1.disable_ipv6 = 1
If some of these are not 1, you can force them to 1 with something like:

sysctl -w net.ipv6.conf.enp89s0.disable_ipv6=1
Check again:

sysctl -a | grep disable_ipv6

Restart system to be sure