Found an interesting half-solution for apps that use Bluetooth: Reset the Security & Privacy settings for this app in Bluetooth section. Background: Custom QT app for custom BLE device. The app crashes when connecting to the device. After Monterrey 12.1 update the app started working, but for the first run only. Reinstalling the app didn't help. It was accidentally found that when a prompt about "APP would like to use Bluetooth" is shown and agreed - the app is able to safely and soundly connect to the Bluetooth device. Once the app is closed these settings must be reset manually for the next run.