I used to work only with Inkscape for a long time but now have Illustrator and am trying to get some of my files into Illustrator to work with them/update them. I have tried saving as an svg (optimized and regular), pdf, and eps and while I can open all of those files in Illustrator, it always saves as a single layer, merging all visible layers into one single layer. I've looked at all of the options and I don't know if I'm just missing something but I didn't see anything there. There are several files that I need to preserve the layers on so if someone could help me with a way that I could possibly save this in Inkscape and open it in Illustrator (or Photoshop) with the layers intact, that would be amazing. Thank you!
As layers in Inkscape are just SVG groups, your Inkscape layers should theoretically be available as separate groups in Illustrator.
While Inkscape supports importing Illustrator files with layers, Illustrator does not support Inkscape files with layers.
If you optimize your files on exporting from Inkscape, layer groups may be lost, depending on the settings for the export (options for collapsing groups and creating groups for objects with similar attributes can cause re-grouping and thus, breakage of layer groups).