There will not be a 2015 version for Mac due to some library incompatibilities, but we are working on it for 2016.
Probably your Linux setup uses a simple Mesa driver, this will be very slow. You will be able to see this in the Help/About box. You should upgrade the driver to the NVidia vendor driver, then you will see a dramatic improvement. Also remember to turn shaders back on, in case they are disabled now due to the low-end driver - check in the About box and/or File/Preferences menu under the Graphics tab.