I am playing with a group on 2.0. We recently made it to Fulgora, only to find out that our gun turrets are incapable of harming the defense drones; The bullets phase right through them without doing any damage and the turrets just sit there spamming bullets at the drones forever until the drone's missiles finally destroy them.

We have Distant Misfires (https://mods.factorio.com/mod/distant-misfires) installed which I presume is what's causing the issue, but it's worked fine with other modded enemies (and they CAN still destroy the hibernation pods) so I don't know if the drones are just set to ignore projectiles or something?

Unfortunately this looks like a bug with Distant Misfires, as it affects any flying enemies. I was able to replicate this just using construction bots and destroyer bots on an enemy force. There just aren't that many mods that have flying enemies, so this fell under the radar.

If you do have a flying enemy that is being hit, I can test that and see how that works. I checked Fulgoran Enemies, but unfortunately their flying drones can't move over the void of space with their collision layers. Phoenix also doesn't get hit by bullets.