Sad to say, I do have a Mastermind TCU. I found a discussion that confirms what you imply, that BLEvo is not compatible with Mastermind TCU, and it probably never will be:
BLEvo Game Over (with MasterMind TCU) - EMTB Forums
Dear BLEvo riders, Writing this message to all of you is hard and painful for me. As most of you know, I bought my first Levo in September 2017. After having previously built an app that connected to a Bluetooth device (for my “real” job), I decided to develop the BLEvo app as a hobby. I...
www.emtbforums.com
Apparently the reason is encryptions added to the Bluetooth protocol due to regulatory concerns. I can sort of understand that, but the fact that Spec's own limited app doesn't even work as advertised just adds insult to the injury of losing BLEvo.
