Volumetric Lighting works with minor changes on 4.18 and 4.19. I have it running on 4.19 atm as well but still need to fix few profiler macros, I might push it into my 4.19 GW merged branch eventually. My 4.18 port of Volumetric Lighting is included in (which includes UE 4.18.3, Blast, Flex, Flow, HBAO+3, VGXI1 and Volumetric Lighting).
My 4.19 Gameworks merge () currently has UE 4.19.1, Blast, Flow, Hairworks 1.4, HBAO+4, TXAA3 and VXGI2 and includes latest fixes from nvidia and one crash fix from me for Flow.