After few weeks of using m0, the biggest issue for me is the quality of Bluetooth connection.
I have Sony WH-1000XM3 headphones and LDAC (in all 3 modes) or AptX is problematic.
I use flac files only, with 900kbps and higher bitrate.
While playing, there are random glitches/pauses of sound (occurs 2-3 times per song, very short stop/glitch), sometimes it behaves like glitch and sound fast forward then.
I have 2.1 firmware - somebody has complained about this issue already here and firmware update has been recommended to him. Occuring also on 2.1.
On AAC and SBC bluetooth mode I had no problems like this.
I look forward to next upgrade, BT on LDAC and AptX is m0 weakness now and I can't use my beloved Sony noise cancelling headphones on a full potential.
I have bought also iBasso IT01 headphones. m0 works flawlessly with wired headphones. Great sound on these IT01 btw.
There is no filter functionality while having BT headphones connected. I don't know if this is normal or another issue...
Works fine on wired connection.