I used this mod to stop Advent propaganda at once. At the XComDropshippropaganda config file, just paste the following at the end and enjoy some silence:

; Vanilla / WOTC missions
+SkipNarrative=SecureUFO
+SkipNarrative=NeutralizeFieldCommander
+SkipNarrative=NeutralizeTarget
+SkipNarrative=NeutralizeTargetVehicle
+SkipNarrative=SabotageTransmitter
+SkipNarrative=SabotageAlienFacility
+SkipNarrative=AdventFacilityBLACKSITE
+SkipNarrative=AdventFacilityFORGE
+SkipNarrative=AdventFacilityPSIGATE
+SkipNarrative=CompoundRescueOperative
+SkipNarrative=ExtractVIP
+SkipNarrative=RescueVIP
+SkipNarrative=Rescue_Vehicle
+SkipNarrative=Terror
+SkipNarrative=ChosenRetaliation
+SkipNarrative=SwarmDefense

; LWOTC missions (if you are playing long war, of course)
+SkipNarrative=RecoverItem_LW
+SkipNarrative=RecoverItemADV_LW
+SkipNarrative=RecoverItemTrain_LW
+SkipNarrative=RecoverItemVehicle_LW
+SkipNarrative=RecoverFlightDevice
+SkipNarrative=HackWorkstation_LW
+SkipNarrative=HackWorkstationADV_LW
+SkipNarrative=HackWorkstationTrain_LW
+SkipNarrative=DestroyRelay_LW
+SkipNarrative=SabotageTransmitter_LW
+SkipNarrative=ProtectDevice_LW
+SkipNarrative=SupplyLineRaidATT_LW
+SkipNarrative=SupplyLineRaidTrain_LW
+SkipNarrative=SupplyLineRaidConvoy_LW
+SkipNarrative=SecureUFO_LW
+SkipNarrative=ExtractVIP_LW
+SkipNarrative=RescueVIP_LW
+SkipNarrative=RescueVIPVehicle_LW
+SkipNarrative=NeutralizeTarget_LW
+SkipNarrative=NeutralizeTargetVehicle_LW
+SkipNarrative=SabotageAlienFacility_LW
+SkipNarrative=Terror_LW
+SkipNarrative=Defend_LW
+SkipNarrative=Invasion_LW
+SkipNarrative=AvengerDefense_LW
+SkipNarrative=SabotageAdventMonument_LW
+SkipNarrative=AdventFacilityBLACKSITE_LW
+SkipNarrative=AdventFacilityFORGE_LW
+SkipNarrative=AdventFacilityPSIGATE_LW
+SkipNarrative=CentralNetworkBroadcast_LW
+SkipNarrative=AssaultAlienFortress_LW
+SkipNarrative=AssaultAlienBase_LW
+SkipNarrative=Rendezvous_LW
+SkipNarrative=TroopManeuvers_LW
+SkipNarrative=Jailbreak_LW
+SkipNarrative=SupplyExtraction_LW
+SkipNarrative=SmashNGrab_LW
+SkipNarrative=AssaultNetworkTower_LW
+SkipNarrative=IntelRaid_LW
+SkipNarrative=SupplyConvoy_LW
+SkipNarrative=RecruitRaid_LW
+SkipNarrative=CovertEscape_LW
+SkipNarrative=CovertEscape_NonPCP_LW
+SkipNarrative=ChosenStrongholdShort
+SkipNarrative=ChosenStrongholdLong
+SkipNarrative=ChosenAvengerDefense
+SkipNarrative=ChosenShowdown_Warlock
+SkipNarrative=ChosenShowdown_Assassin
+SkipNarrative=ChosenShowdown_Hunter