Hi @udi.mosh.
Could you please clarify the “111 error”, since it is nothing I recognise or familiar with. Where is this error originating from, and are you able to provide the log file or error messages associated with it (or at the very least, a screenshot)?
You don’t have to use a central authentication mechanism, no. You can configure the accounts on each agent server individually. This can be inefficient for larger systems, though.
Normally, the master will choose which agent to start the session on, based on load. So a user logging in may end up on any one of the agents.
However, it is possible to configure ThinLinc so that each user has a dedicated agent, by using the subcluster functionality. See Configuring ThinLinc Servers in a Cluster — The ThinLinc Administrator's Guide 4.16.0 build 3491 documentation. So if you had a cluster of 5 agents, you would essentially configure 5 subclusters, each with only one specific user being allowed access.
As above, I’m not familiar with the 111 error, so will need more info. But valid TLS certificates are not a requirement. ThinLinc ships with self-signed certificates which will work, although most browsers will raise a warning.