Fixing Bluetooth instability on Ubuntu (26.04) caused by Realtek RTL8821CU Wi-Fi/Bluetooth combo chipset

A developer resolved Bluetooth instability on Ubuntu 26.04 caused by a Realtek RTL8821CU Wi-Fi/Bluetooth combo chipset. The fix required disabling the Wi-Fi interface on the Realtek device using a systemd service to keep it offline at startup. The solution was documented after extensive searching through Stack Overflow and Reddit posts.

I got a pair of some nice sony 1000xm6 headphones which i wanted to connect to my computer running ubuntu. To connect my headphones with my computer i purchased a Realtek RTL8821CU which has a chipset that is integrated with wifi and bluetooth. To my bad luck the headphones did not connect gracefully to my bluetooth device. The headphones connected without any issue to other devices so i was sure that they were fine and the issue was lying somewhere between ubuntu and the realtek device. And so my journey to fix the issue had started. I tried google, chatgpt, gemini and any LLM you can think of. Sadly none of these seemed to have a solution so i had to dig deeper to the depths of stackoverflow and old reddit posts dating years back. After a lot of searching i felt obligated to post the solution i found here for anyone stumbling on the same issue. It seems that ubuntu doesn't play well with bluetooth headphones that connect to a dual integrated chip for wifi and bluetooth so all i had to do what disable the wifi from the realtek device and just use bluetooth this way: Search for your wireless network interfaces iw dev Close the wifi connection from the device sudo ip link set wlx90de80ee7e03 down To keep the device wifi offline you can start a service to keep it off on startup sudo nano /etc/systemd/system/disable-realtek-wifi.service Write inside this file Unit Description=Disable Realtek WiFi interface After=network-pre.target Before=network.target Service Type=oneshot ExecStart=/usr/sbin/ip link set wlx90de80ee7e03 down RemainAfterExit=yes Install WantedBy=multi-user.target And enable the service sudo systemctl enable disable-realtek-wifi.service