I am trying to use speedtree models (more precisely, the free ones you can download from their website) on iOS devices, and I am running into a number of problems.
First, I removed all speedtree-specific nodes from materials because I was not sure they were supported, so I ended up with materials using just diffuse, normal and (vertex-based) AO (I tried also to remove the AO). The trees were rendered just fine in the UE4 mobile preview, but not on the device, where I was basically just seeing a grey trunk (leaves are entirely made of billboards).
From various searches in UE4 answerhub and forums, the problem could be related to the fact that speedtree models use 8 UV channels, while iOS devices support far less channels. By switching to Metal rendering, I can see the leaves (probably because more UV channels are supported), but texture UVs are messed up, presumably because some UVs are larger than 1 (see this question).
Since various UE4 samples include trees that were presumably made with speedtree, and these samples work just fine on mobile, I was wondering how these trees were prepared for mobile, and more generally, whether anyone has been able to use speedtree models on iOS devices.