With the latest Tumbleweed snapshot 20240808 the behaviour changed a bit. Now my dispatcher script completes before the final suspend. Umounting nfs shares doesn't succeed, though, because a few seconds before NM is removing the DHCP settings from the network interface. I am not sure, why the behaviour changed at all, because the latest NetworkManager rpm was not part of this snapshot, but of snapshot 20240730, and I definitively had the former behaviour til snapshot 20240808 was installed.