I have just bought next inexpensive Xperia M5 phone with pretty nice hardware. However I already found those things to be missing or deliberately removed:

• USB OTG does not work (solved).
• CardBoard VR does not work.

Update regarding USB OTG – “it’s not a bug its a feature” – after you connect a USB device using OTG cable you need to run “Detect USB device” application that will make OTG work. Considering security this may be a good choice to allow external devices by hand.