Announcements activation after next server start

[S-S-X]

Simply that, announcement is about significant configuration change or other thing that affects game play enough that players should be notified about change.

But when change is actually in effect only after next server restart because configuration, mods or something has to be reloaded it makes more sense to also allow inform players only after server has been restarted.

Probably best way to do this is to use counter (simple 1/0 is fine for basic use), could set counter to 0 at first and increment it using minetest.register_on_mods_loaded callback.
Add announcement only if counter is higher than 0 (if there's any reason then announcement could also have different value set in future).