Controlling SMB Dialects

Zenhawk: you can do SMB dialect mandating at the SMB client level since Windows 10 Version 1709 and Windows Server version 1709 (so including WS19). You can set a minimum and maximum SMB version number, for example 3.0.2-3.1.1. This way you can avoid SMB 3.0, although you also prohibit lower versions at the same time.

If your intention however is to do this mandating at the SMB server level (on Windows client and Windows Server), it's indeed not possible, just as Ned already said. However, if you can do mandating for every system that can access a certain SMB server, the mandating is de facto in place for the SMB server as well. For example, suppose you have an environment with a WS19 server, where the only set of systems able to access its SMB server are W10/WS Version 1709+ or W11 systems, then you could configure the mandating on these systems so that SMB 3.0 will never be used by the WS19 SMB server. But this is no hard configured SMB server way of course, so pay attention (e.g., if a new system without mandating set joins that set of systems, the situation can change of course, possibly introducing SMB 3.0 again!).