Opening /dev/cu.vLinkerMC @ 38400 baud (settle 2.0s)...
-> b'ATZ\r'
<- nothing received in 5.0s

This means the adapter itself never answered -- the problem is upstream of tunie (the OS<->adapter serial/Bluetooth channel), not in tunie's protocol handling. Re-pairing the adapter (forget it in Bluetooth settings, pair fresh) is the next thing to try, not a tunie flag.

(full session log: logs/tunie-raw-20260826-202441.txt)