We love Bandlab, but it is tough not to have a better microphone or headphones available, especially with just one lightning connection on the iPHone. Well we have tried the following below from Amazon and it is working great with your Yeti Microphone and our 3.5 mm headphones.
USB 3 Camera Adapter,3 in 1 USB Female OTG Adapter with Charging and 3.5mm Headphone Audio Jack Splitter for iPhone/iPad,Support USB Flash Drive,MIDI Keyboard
Make sure to note that you if you plug in the lightning cable to power your phone (the third plug on the adapter) you will lose your 3.5 mm headphone so don’t do that when you are recording. It has been working great for us so far and good luck recording!