From local machine
wget https://raw.githubusercontent.com/Realtek-OpenSource/android_hardware_realtek/rtk1395/bt/rtkbt/Firmware/BT/rtl8761b_config
wget https://raw.githubusercontent.com/Realtek-OpenSource/android_hardware_realtek/rtk1395/bt/rtkbt/Firmware/BT/rtl8761b_fw
scp ./rtl8761b_config user@host:~/
scp ./rtl8761b_fw user@host:~/
From ubuntu core machine
sudo mkdir ~/firmware
sudo cp -r /lib/firmware ~/firmware/
cp ./rtl8761b_config ~/firmware/rtl_bt/
cp ./rtl8761b_fw ~/firmware/rtl_bt/
ln -s /home/user/firmware/rtl_bt/rtl8761b_config /home/user/firmware/rtl_bt/rtl8761bu_config.bin
ln -s /home/user/firmware/rtl_bt/rtl8761b_fw /home/user/firmware/rtl_bt/rtl8761b_fw.bin
$ sudo cat >> /etc/systemd/system/customdrivers.service <<EOL
[Unit]
Description=Bind mount /lib/firmware
Before=systemd-networkd.service
[Service]
Type=oneshot
ExecStart=/usr/bin/mount --bind /home/user/firmware /lib/firmware
[Install]
WantedBy=multi-user.target
EOL
sudo systemctl enable customdrivers
sudo systemctl start customdrivers
sudo dmesg -c
sudo reboot
sudo bluetoothctl
power on
scan on