I agree! What a PITA and a waste of money.They made it so weird with Hero5 and later models with that bulky $50 microphone adapter plus cost of mic and wiring to get external audio on later Hero models.
I have access to an older Hero 3+, as well as a cheap lav mic and adapter. I think I'll rig this up for some testing this weekend, and once I decide on a camera, I can just swap things out.
Still really leaning towards the Osmo though. They're offering 5% off through their website, as well as a free battery / charger upgrade with purchase. Then consider that the mic adapter is $17 on Amazon.. Kinda seems like the way to go.