Hi Peter,
I think that you replied to me via personal mail, so I have brought your query back onto the forum here.
I have attached two photographs of my arrangement; one showing the components disconnected, the other showing the components connected.
For my setup,
1. Arktek USB A to USB C converter
2. Cubilux USB C to 3.5mm DAC unit
3. 3.5mm mono to 3.5mm stereo cable adapter (this was included with item 4 below)
4. KitSound Bluetooth Airline adapter
This works very well with my August EP650 Bluetooth headphones. For some reason, since using this setup, I have stopped being hit by jet-lag, from which I used to suffer really badly!!
Hopefully this will give you a 'starter for ten'. Some of my elements are quite old now so you might find newer and potentially better items. I must say that I'm very pleased with this setup.
Also, although I have this setup to hand, I also use the newly provided BB1 direct Bluetooth system. This, for me, is especially good when I'm on long distance flights where I don't need the WiFi element. Somewhat more tidy when in a tight space such as an aircraft seat.
Regards,
Peter.