I downloaded BMC3 1.19.2 with my friends on aternos, it seems like there is no dragons, I played older versions of bmc before and had bunch of dragons now it is impossible I looked everywhere, underground, nether, chests, it's just not spawning...

I am not sure what mod was previously included that spawned dragons, but this mod does not. To spawn dragon eggs in chests you will have to enable the option in the mod's config. Otherwise, you can get an egg from killing the end dragon and hatch that.