[Razer Phone 2 Guides, News, & Discussion] LSS4181:
It seems deleting BluetoothResCommon.apk prevented bluetooth from starting up with logcats complaining about HID-related issues. It's possible that the vendor partition might not have the drivers and related stuffs meant to support HID devices (maybe this means gamepads won't work, I need to confirm this as I do have a gamepad that I intend to use it with).

The decompiled BluetoothResCommon.apk contained these in bools.xml, which seems to indicate that it doesn't support connecting HID devices.

<?xml version="1.0" encoding="utf-8"?>
<resources>
<bool name="profile_supported_hfpclient">false</bool>
<bool name="profile_supported_avrcp_controller">true</bool>
<bool name="profile_supported_a2dp_sink">true</bool>
<bool name="profile_supported_sap">true</bool>
<bool name="profile_supported_ba">true</bool>
<bool name="profile_supported_hid_device">false</bool>
</resources>

And as for RazerAuraBluetoothRes.apk, the decompiled content has an integers.xml which contained values setting the codec priority for aptX-related ones to -1 (which probably means it would never try to use them).

<?xml version="1.0" encoding="utf-8"?>
<resources>
<integer name="a2dp_source_codec_priority_aptx">-1</integer>
<integer name="a2dp_source_codec_priority_aptx_hd">-1</integer>
<integer name="a2dp_source_codec_priority_aptx_adaptive">-1</integer>
<integer name="a2dp_source_codec_priority_aptx_tws">-1</integer>
</resources>

I tried reflashing the GSI (Havoc 2.9, 20190914) after deleting BluetoothResCommon.apk and still cannot turn on Bluetooth.

Bluetooth can be turned on if BluetoothResCommon.apk is kept, but my aptX-capable headset (CX SPORT) can only handle phone calls, media audio cannot be routed as a2dp initialization failed somewhere (and nothing apparent shows up in the logcats I captured).

Maybe instead of deleting the overlays, hacking them (by changing their values so things can work) might be a better idea...

EDIT: DO NOT DELETE BluetoothResCommon.apk, but you can hack it by setting all the values mentioned to true (with the help of apktool). Not sure about before, but with the hacked BluetoothResCommon.apk, I can turn on Bluetooth and pair my FeiZhiWee 2T bluetooth gamepad just fine (although it won't be of too much use since I cannot toggle SELinux to permissive with arter97's kernel).

Note that if you intend to hack the overlays, you need to pay attention to this after rebuilding with apktool (that you need to copy the original META-INF and AndroidManifest.xml), or you may get a bootloop.

However, with or without RazerAuraBluetoothRes.apk, the issue that I cannot route media audio to Bluetooth headset, only phone calls, on Havoc 2.9 GSI, is still there. It seems toggling media audio also takes a long time (and logcat showed something about timeout). The toggle itself works as usual but in reality media audio doesn't work.

EDIT 2: I'm new to the A/B partitioning scheme. Can the contents in the inactive slot affect the other? I only flashed the kernel and GSI (and modified vendor contents) in active slot (A) while keeping the inactive slot (B) intact (with stock stuffs just in case).

EDIT 3: I have confirmed that deleting both BluetoothResCommon.apk and RazerAuraBluetoothRes.apk does fix the media audio, but it must be done before first GSI boot. If you have booted, you won't be able to turn on Bluetooth anymore once you delete BluetoothResCommon.apk. You'll need to do a factory reset (wipe data from TWRP) and clean flash the GSI.