I also have a Meridian Explorer2 (ME2) and use it occasionally with Android, mostly with an Acer tablet as a source, once in a while with a DAP (FiiO X5III). I mostly use UAPP streaming Tidal and sometimest other Android players for local music. I have no experience with Qobuz.
My tablet set up is: Tablet--> USB out --> ME2 --> line out of ME2--> Schiit Magni 2 Uber Amp.
The ME2 is definitely dependent if the source can provide enough power out of its USB for it to work properly. I always feel that if I can't get the thing to work properly (more to do with the FiiO) it's because of these USB power issues. There is a Youtube video from a few years back of someone demonstrating the ME2's use as a DAC in Android using UAPP.
Sometimes when the connection goes bad I have to disconnect the ME2 and reconnect, or restart UAPP, etc., but usually it eventually reconnects. It's not an ideal, stable setup all the time but mostly works once it's got a good connection.
As far as Spotify goes: Spotify Android app is not set up to recognize a USB output in my experience. UAPP and some other Android local music players like FiiO Player, Onkyo HF Pro, Neutron, etc., can handle a USB connection, but I've never had any luck with Spotify; it's just got to be outputted per the normal headphone out or line out.