SOUND

Slow Speech
If using Mint Mobile and hearing slow speech, set the APN Protocol to IPv4.
On B1-Plus: Settings / Network & Internet / Mobile Network / Advanced / Access Point Names / T-Mobile US LTE / APN Protocol / IPv4

Volume Boost
Feature added v13.26.
Available via OPTIONS button
To unboost, turn the volume knob counter-clockwise

Bluetooth
Unfortunately, Bluetooth audio available only on Android side (smartphone, apps) and does not work on the RFinder side.
There's been chatter about RFinder creating a Bluetooth dongle for the RFinder side.