I created two Jungle dimensions, both of which seem to not generate a starting platform I can teleport to. I can't judge if I am just unlucky or this is a general issue with Jungles. I would expect that at the very least, if the platform can't fit on the ground, I get one in the treetops.

This can be an issue of a jungle tree overwriting the platform. Easy to fix however. Just send over a fully charged new matter receiver to that dimension using the Dimension Editor. Then you can dial to it