Great, Andrew! Good to hear, that there’re some other activations being done with digital voice modes. I’m always carrying various digital HT’s with me (DMR, TETRA, APCO P25, Fusion, D-STAR), also during SOTA activations.
But it’s always difficult to find somebody for a simplex contact. Until yet, I worked chasers on TETRA, DMR and D-STAR from two or three SOTA summits in simplex on UHF, e.g. DC5CC in TETRA and DMR from DL/MF-079, Wendelstein (SOTA Database).
DMR, TETRA and APCO P25 radios have to be programmed in advance using a CPS with the right frequencies and talkgroups, timeslots, ColorCodes etc. It’s important to program the national CoA frequencies for simplex in advance. (Germany+Austria: DMR (TS1 TG1/TG9 CC1) and C4FM: 433.450 MHz, TETRA (MCC:901 MNC:16383 GSSI:1): 430.4125 MHz). Keep that in mind.
I’m really looking forward to more DMR, TETRA, APCO P25, Fusion, D-STAR chasers! 
73,
DK3CW, JP