EDIT
When I connect the Beatstep to AUM on my iPad (throw a USB hub) and the TM too (with the MIDI in jack, not the USB port due to this issue, it works “quite” good. Quite because the knobs are OK : value are changing in the performance effect but when I activate a pad (i.e. pad 1 for track 1,…), the track label doesn’t into red as it does when I push the corresponding button directly on the TM. THe result is just changing the pattern number from 1 to 128. I thing it’s due to the value’s panel of the pad in the Arturia software, from 0 to 127.
So, I’ve to continue investigating, but it’s better than before.