Hi there,
So , First I doubt the Juice is worth the squeeze… Results are hit and miss, not really meant for it, I think soon there will be another option that can choice between Internal or EXT, like on the C6. I wouldn’t waste my time the circuit has to be carefully tuned as not to damage the Xiao.
Not all those antennas’ are created equal, DON’T use one for Lora, meant for WiFI or visa-versa.
HTH
GL PJ
BTW, Nordic makes a range booster chip for BLE, seeed may offer a sandwich board for it would be great.