So this is fixed in the main branch on GitHub but not released as a stable version yet. I went ahead and updated my install and got it working.
I have an install on Debian 11, not using any authentication. Here is what I did.
systemctl stop guacd
git clone git://github.com/apache/guacamole-server.git
cd guacamole-server
autoreconf -fi
./configure --with-systemd-dir=/etc/systemd/system
make
make install
systemctl enable guacd
sudo reboot