Finally, got the CyanogenMod CM 12.1 on Sony Xperia ZR upgrade for Sony Xperia ZR (Dogo). Definitely, far superior to the Sony Xperia Stock Lollipop firmware. Upgrading from KitKat to Lollipop when the Stock Firmware was released way back in May broke my phone’s Wireless 2.4 Ghz band and I was forced to use the 5 Ghz band to connect to the Internet. Luckily, the router I had supported this arrangement.
After unlocking the bootloader and installing CyanogenMod CM 11, no luck with 2.4 Ghz Wireless working, but after installing the latest CyanogenMod CM 12.1 on the Sony Xperia ZR, wireless 2.4 Ghz works very well. I suspect the Sony Xperia ZR stock firmware updates are borked. But no one on the Sony Mobile forums acknowledges that.
Now that I have a working 2.4 Ghz wireless it is worth moving over to CyanogenMod 12.1. Not sure if the Sony Xperia ZR will see Android M, anyway.