Segger
Focus on j-link
YouTube channel: https://www.youtube.com/playlist?list=PLDqLs4CjhqjEPT3ltdY7W4Sa8aWfL9-4G
Appears that they compete with IAR i-jet: https://www.youtube.com/watch?v=DdtkMd9YTkA
Counterfeit
Unfortunately there are many fakes out there. This is like a combination of their popularity and that most of the value is in the software more than the hardware. Since the software is licensed based on the hardware you have, there is a high incentive to clone them.
I (mcmaster) bought one off of eBay and didn't know it was a clone at the time. Some notes:
- Device initially worked with Segger a bit, but produced a warning (something like "faulty hardware detected, please contact support")
- Firmware upgrade essentially bricked the device. Linux lsusb still showed it, but Segger software no longer detected it