The challenge does not require jumping from the highest point of the facility. The highest point - the large petal array - is probably too far away to make the jump without mods. The solidified lava on the other bank is not sufficient, nor is landing on the raised island in the middle. An Acrobatic Oz Kit makes this much easier, but is not necessary.
The jump is possible from the top of the yellow onion dome (one of two) nearest the river. (This is probably the only point from which the jump can be made.) Its top is easily accessible by an O2-assisted jump from the main petal array. Once there, a running jump off the edge, plus an O2 boost halfway through the jump (when the jump has lost nearly all of its forward momentum, but not so late that too much height is lost), should be enough to land safely on the cliff directly opposite the dome.
Players have reported getting the challenge even if the character touches the other side without landing on it before falling into the lava.