28.4 has not fixed the same Bluetooth problem for me using a Google Pixel 4a. As mentioned by others, the BT connection may drop after some seconds, or it shows in the RV3 app that I have a BT connection but on the Android device it shows that there is no other device connected via BT. Also, I am never prompted to enter the PIN for the initial connection. I usually use Lefebre NTRIP with 3rd party software, but the current problem makes this workflow unusable.
Android is a very flexible system, and Android devices from different manufacturers operate slightly differently too. Changes in Bluetooth behavior were introduced from the Android side. We try to support these changes from the Reach side to keep your workflow usual. But it’s hard to test the compatibility with all existing Androids. Moreover, we’ve tested 28.4 with Google Pixel, and the Bluetooth issue has gone for our office phones.
I mean, we need to examine what happens with your phone exactly. Please share the Full system report from your Reach at email@example.com.