RTL8821CU and other BT dongles not working via OTG on R36S Plus BoyHom (Got it working!)

[KalleTheodor]

Hello,
I’m using the R36S Plus from BoyHom and would like to add Bluetooth support.
For this I bought an RTL8821CU dongle.

Problem:

As soon as I plug in the dongle, my WiFi connection drops completely.

In the WiFi menu it only shows “%” instead of available networks.

The same happens when I try with a Bluetooth-only dongle.

I already tested several ArkOS distributions, always with the same result.

Expected behavior:

WiFi should continue to work while the BT dongle is active.

What I’ve tried so far:

Different ArkOS versions

Multiple dongles (RTL8821CU + Bluetooth-only dongle)

Question:

Is there any solution or workaround to use Bluetooth alongside WiFi on the R36S Plus?

[KalleTheodor]

I flashed a completely new firmware, and with that, the dongle worked immediately.

The root cause of the issue was the onboard WiFi module, which was blocking OTG.
After desoldering the onboard WiFi chip, OTG started working right away.

I've now soldered the 8821CU module directly onto the board.
Important: The 5V connection is only needed if you're using a disassembled USB dongle (i.e., wiring the chip directly).
Do not use the 3.3V line from the original WiFi module — it won’t power the dongle correctly.
Instead, find a proper 5V point on the board (see red wire in the photo).

Everything is working smoothly now. Hope this helps someone running into the same issue.

[basilpolicy]

Where did you obtain this module?

[KalleTheodor]

I obtained the module as a USB WiFi/BT dongle (it needs 5 V).
When you get the board, you can also simply swap out the onboard WiFi module.

Here are two pictures for clarification:

• USB dongle (5 V):

• Board E103-RTL8811CU with 3.3 V WiFi module:
  Datasheet (EBYTE Modul)