if you get/have AAWireless dongle you can set it to only connect when it also connects to the radio Bluetooth.

If not You can get a toggle switch USB cable to make disconnecting easier.

Have not tried, but Sonoff has a usb switch that you can control remotely and could potentially use Google Home. https://sonoff.tech/product/diy-smart-switches/micro/

The good news is anyone can grab the GrapheneOS PDF viewer. https://github.com/GrapheneOS/PdfViewer Or from the Google Play store https://play.google.com/store/apps/details?id=app.grapheneos.pdfviewer.play