Connect Guacamole on Docker to Ubuntu 20.04 LXC Container

I could use some pointers (advice/resources) about establishing an RDP connection between Guacamole set up with Docker containers and a Linux container running ubuntu 20.04.

Guacamole is an Apache product that allows the user to access a desktop remotely using just a browser.

Since Brian Mullan’s CIAB setup inspired this endeavor, the Linux container is named ‘cn1’.

When I try to connect to cn1, I receive an error message telling me that cn1 is taking too long to respond.

cn1 has xrdp installed, but no Guac elements.

The host for the containers is running Ubuntu 20.04 (newly-installed).

The Docker containers have their own network (172.xxx…), which is visible to the host. It also has its own bridge. The LXC’s ip address is 10.xxx…, also visible to the host. Its bridge is named lxdbr0.

I can ping between all three elements: host to containers, Docker to cn1, cn1 to host, etc.

I can connect to cn1 from the host using Remmina. Once connected, I can access the internet from cn1.

In Guac’s ‘Connections’ setup, I used cn1’s ip address and port 3389.

No joy when I try to connect though.

The well-known problem of Docker changing the iptables seemed like a possible reason for this problem, but being able to access the internet from the Linux container doesn’t seem to fit the symptoms of the iptable problem.

Thoughts? Links to resources/tutorials? Has this question already been answered somewhere?