Found this in the log of server version 3.12.1 - which by the way has been released in stable mode but is not added here.
Looks like the permission system for the new client is coming! YEAH!!!
(The server says 3.12.1 - the log still says 3.12.0)
Server Release 3.12.0 31 March 2020
- Fixed bug related with new TS5 Client Permission Manager