exotics

[cerulean lagoon]

are legend lost sectors the only way to get new exotic armor pieces?

[wet shoal]

mostly yes, some exotics still drop open world. but it's much better to farm lost sectors

[edgy dome]

you can get the "old" exotic armour from any exotic engram, but the "new" ones (post WQ) you have to unlock by getting them

in a lost sector first, after that they can also come from random exotic engrams

iirc vex incursion can also drop the new ones, but im not 100% sure