I don't think Android to Android MTP works on any device.
The fastest way is going to be to transfer the data to a PC/Mac using MTP and then to the Q10 using a USB stick.
For Photos, Music and small media files I am using the HDD in my Media Player as the central storage. It is connected via Samba (as a Server) to my PC.
So when I download info from my Phone to my PC it is implicitly shared also with my Android player as both share the same HDD. Even my old one is fast enough for that.
Obviously you may access the Internal HDD also directly via Samba Client on your phone, but that is not for everybody, use the way which is most convenient for you.
Quick and easy. Use this PC to make safety copies to where ever (cloud) or on whatever media. NAS would do the same for you but more complex and yet another box you really don't need (anymore).