The Mercusys MA530 Bluetooth USB adapter (VID:PID 2c4e:0115)
is based on a Realtek RTL8761BU chipset.

Adding:

     { USB_DEVICE(0x2c4e, 0x0115), .driver_info = BTUSB_REALTEK },

to drivers/bluetooth/btusb.c allows proper firmware loading
(rtl8761bu_fw.bin) and stable LE discovery.

Without this entry, discovery repeatedly toggles on/off.

Tested on Debian 13 (trixie), kernel 6.12.73+deb13-amd64.

Hi

Thanks for reporting the issue with the specific device.

Such requests need to first add support upstream, a patch has been
posted in
https://lore.kernel.org/linux-bluetooth/20260214215815.26248-1-edo@akse.cloud/
but needs first to be accepted.

Adding accordingly metadata so we can track the progress upstream.

Regards,
Salvatore