Here it was (is) possible to receive mux T2_MI on 10998 H, 15282,3/4,8PSK, which I didn't initially think was possible with my antenna.
Of course, the signal is at the limit; it is enough to lock a PLP 0 stream and see that I was not wrong when I suspected it was a Russian mux, but then I could not lock it. The confirmation is on FlySat, reported by Edward.
So the situation is not as desperate as I thought at the beginning, but with a bigger antenna, one can hope for more from this beam #1, which does not have coverage in Europe's central and western areas.
I forgot that the easier-to-lock Russian mux is on 10852 V,1808,3/4. It is a radio package.