2000 i30 with 93K miles, always had some minor strut suspension noise since I bought it at 70K, not major enough to worry. A week ago, started to hear some bad metallic rattling/clanking coming from the front passenger wheel area, sounded like your typical sway bar link issue so I did some investigating, still can't figure out. Here's a list of what I tried and results/observations.

At its worst, sounds like a marble rattling around in a felt-lined coffee can. LOL
Happens worst on rutted/rippled city roadways.
But, still happens on what appear to be smooth city roads, but not as often.
Steady highway driving at 60mph doesn't make the noise unless you hit rippled roadway.
If I accelerate HARD over rough pavement, rattling doesn't really happen, but as soon as I release the accelerator, the sound returns.
If I brake HARD over rough pavement, rattling doesn't really happen, but as soon as I let go of the brake, the sound returns
The last two are really the same thing (axle loading), just in opposite directions!
While coasting on smooth road at about 15mph in neutral, shifting into drive causes one clank/rattle, and no more until you hit ripples.

I've started with cheaper fixes:

Tightened any loose hoses, brackets, accessories.
Sway bar links felt worn. If I grabbed one with both hands, and moved it up and down, there was clicking due to worn ball/socket. Replaced the links - no effect.
Replaced caliper pins/bolts and greased them well - no effect. (thought maybe caliper was bouncing around)
Replaced brake pad slide clips - no effect.(thought maybe pads were bouncing around)
Strut mount appears OK, no vertical or sideways movement from bouncing or careful prybar tests.
Ball joint appears OK after prybar tests
Swaybar bushings look good.
Rubber gasket on strut coils properly installed, no spring to seat metal contact.
Passenger motor mount visually looks undamaged. Prybar tests show some movement, but no sounds of any kind.
Struts are not leaking (Nissan's way of checking for bad struts), nor are they loose or wobbly.
Tie rod end has no vertical movement from rubber mallet.
Tied rod end does make a click if you rotate it front to back (while keeping steering straight ahead.
Grabbed tire and shook left-right, up-down and no noise.

I may have missed some observations, but what I am wondering is:

Based on my acceleration/braking tests above, where load on the axles stops the noise, while coasting lets the noise happen, what could it be?
Can you tell if a motor mount is bad by moving the engine with a prybar, or are rips and tears the main giveaway?

well, you did a great job ckecking everything
it's most likely the outer CV axle joint .It's easy to replace. seems like you know enough about cars, i'm sure you can R&R it for free labor.
if you are a 5sp manual trans or automatic, the passenger side axle is the same. if you have swapped in a 6sp manual, you MUST get a 6sp mt passenger mount. Raxles is a good place to start.

I had this exact problem with my 2002 i35. Never figured out what it was. But when I went to replace all 4 shocks/struts, the noise went away.