Guacamole 1.4: “Log in failed” for RDP connections

Problem (Guacamole 1.4 while connecting to an RDP server):

…and in logs:

guacamole guacd[2390]: RDP server closed/refused connection: Security negotiation failed (wrong security type?)

Possible explanation:

• https://issues.apache.org/jira/browse/GUACAMOLE-1249
• https://github.com/SingularityApp/guacamole/blob/main/.graph/Debug/Patch/Systemd%20breaks%20RDP.md

Solution:

nano /etc/systemd/system/guacd.service # replace User=daemon with User=root
systemctl daemon-reload
systemctl restart guacd