Davy,
I have to say I am also getting occasional pops and clicks when streaming Tidal in UAPP on my V30 (Internal HiRes driver, only MQA flag set). Usually it gets better after rebooting the phone, but seems to come back after awhile.
I know you recommend using OkHTTP client, but for me HTTPUrlConnection seems to have fewer clicks and pops. It is clearly worse on higher bitrate MQA tracks than lower bitrate 16/44 tracks. I have a 100mbps internet connection, ping usually in the 10ms range, router in same room.
I've tried different Network chunk sizes (System menu) but doesn't seem to affect it - or at least it doesn't solve it. Network buffer size is 15 seconds (System menu). I'll try raising Buffer size (Internal HiRes menu) as you suggested. It's been at 600ms so far.
I should add that the same issue can occur when streaming in the Tidal app, and I think Tidal's servers may be to blame. But I'd have thought good buffering should prevent it. For Master/MQA tracks I generally download them in the Tidal app instead which avoids the problem. Of course I cannot do that with 16/44 tracks since the Tidal app will send them to the Android Mixer.
If there is anything I can provide that will help diagnose this, please let me know.