QNX was the real-time OS they sold for embedded devices. Modern BB phones used BB11 OS. It had Android emulation but obviously no play store or google services so they had to abandon it. Android BB phones were still great but obviously not enough people cared.
I liked the Android phones. The hub was still nicely integrated, the hardware keyboard had good features. The main problem was that they were expensive and hard to get.
I also had them. The last one I bought turned out to be made for Indian market and had a firmware that was calling 112 every time you looked a it the wrong way. So yeah, it wasn't hard to find one on eBay but it was risky and there were no official distributors in my country any more.
The previous Android BB I had worked fine until the OS died of old age as Android used to do back then. I had no issues with the hardware or security.
I understand you had different experience with them than I did. For me it was the best phone with hardware keyboard at the moment and it worked fine.