The bit they always leave out from bikepacking bike photos is the backpack. I find this super dishonest, because it makes people think they can get away with a much slimmer setup than they really can.
Inside the frame is still the best place. If you are good with your hands, you may be able to make a custom frame bag that fills all the little nooks and crannies in there to maximize bladder space. Note that getting a larger bladder and under filling it will allow it to squeeze into all those places. Platypus bladders have less big chunky stuff on them than Camelbaks.
Look into how big of a water bottle you can fit on the down tube. I can fit a 2L Kleen Kanteen on the downtube of my fat bike. Joe Cruz managed to fit an additional water bottle above that!
Also shown here is the stem cap mounted water bottle that King Cage makes.
Depending on the design of your fork, you can also use hose clamps to attach cages to your fork.