Have a SOLO button for each input channel with the capability to have several channels with the SOLO button active (like there is in the X32, UA Apollo, …..)
I have found a workaround but it is not like a real SOLO feature.
I have created a mute group on all inputs channels including ST, USB, BT and I have mapped this mute group with a soft key. By this way all channels are muted and I unmute one by one the channels that I want in SOLO.
The remaining issues are that if I use again the soft key, all channels are unmuted and potentially I could need some to stay muted and this extra work in the workflow when mixing