I have the same issue after a docker update i could no longer connect to my vnc servers and i have tried everything, even new container with fresh install.
Before the update i was able to connect to my local network and remote VNC servers.
also, i confirm that with RDP i can connect without a problem
i have installed vnc to windows 7, windows 10 & windows 11 machines and i could not establish any connection at all via VNC after the update 22/03/2023 (or 21/03/2023).
i have the same errors as mentioned in previous post
guacd[171]: ERROR: Unable to connect to VNC server.
guacd[171]: INFO: User "@c" disconnected (0 users remain)
guacd[171]: INFO: Last user of connection "$d" disconnected
guacd[24]: INFO: Connection "$d" removed.
I have noticed (if this can help you narrow down the problem) that on my saved connections i have the password saved, so i tried to remove the saved password and see what will happen.
well it did ask me to enter the password but after the password i get disconected and got the above error in the log.