Any good single-player campaigns for it? Call me a retard, but the best part of Operation Flashpoint was the single-player campaign.
99% of my play time on the series was single player and I've been playing it since the first OPF.
There are a bunch of good SP scenarios in Steam workshop, and even conversions of Arma 1-2 campaigns into Arma 3 engine using the RHS mods.
From the dlc ones, I really like aid worker campaing (Remnants of war, I think).
But I can't recommend enough the AntiStasi Ultimate series of maps for single player. It basically turn every map into some sort of persistent military GTA where you play a guerilla vs invaders in missions raging from small fights like attacking an outpost, roadblocks to distribution of goods to gain population support to complex multi-domain operations to capture bases and cities.
IMHO is easily one of the best experiences you can have with the game today.