I'm talking specifically EPA and DHA, neither of which are found in any food source except marine biota.
Microalgae is the only vegan source I know of but it's almost nonexistent in most vegan kitchens and restaurants, nor do I know any vegans who consume it.
Do most vegans just wing it without it, are unaware of it, take pills, or just don't care?
I personally do not worry about the EPA and DHA intake that I have. When I used to care about my Omega 3 (ALA) intake, I consumed a lot of flax seeds and chia seeds which are both pretty high in Omega 3 and also have a good Omega 3 and Omega 6 ratio.
Since you specifically asked for non-ALA answer though, they only feasible way for most vegans to get their EPA and DHA would be through vegan supplements made from the microalgae you mention. To be honest (I do not have the statistics to back this up though) I think that most vegans just don't care about it. For me personally, while I know that having EPA and DHA in my diet would definitely be good, the price I (and more importantly other sentient beings) would have to pay is simply too much. If on one hand I can be somewhat healthier and eat animals and on the other not be somewhat healthier and not eat animals, it is not even something I have to think about. I suspect that many vegan-because-of-their-beliefs vegans will have it similar.
EDIT: I forgot to note that while the ALA to EPA and DHA conversion rates are really bad, the conversion still happens. One vegan way of influencing this would be to lower the amount of Omega 6 from processed food in one's diet as this actually may have inhibiting effects on the conversion process.
I've got a bottle of these in my refrigerator right now. My wife prefers to add ground flax seeds to her food. It's often hard to tell what supplements you might need or what effects the supplements you are taking have on you. It's anecdotal, but the EFA supplements I take, along with a couple other things, seem to noticeably reduce some chronic joint pain issues I have.
Omega 3 is only produced by algae and plants, fish only have it because they eat algae.
If you are worried about EPA and DHA you can make an algae salad with sesame in Japanese style or go to an Asian restaurant.
Nori seaweed is cheap were I live but for the most part I don't worry about this because the body can convert ALA to EPA and EPA to DHA and from 25 grams of flax seeds and chia on top of all the meals I eat in a day I get about 12 times more omega 3 than recommended daily which gets converted evenly.
Also my saturated fat and omega 6 intake are as low as humanly possible.
I take a supplement. I have no idea if I need a supplement because there appears to be no hard data on ALA conversion rates. I might be on the upper end of the curve, but I have no easy way of knowing. I could start eating more sea vegetables. They are abundantly available here in west Houston. Unfortunately, I haven't found any labelled with DHA content. Most are not even differentiated by species.
