The Bose QuietComfort Ultra headphones support various Bluetooth aptX profiles:

- aptX Lossless: these headphones are one of the few products that support aptX Lossless, which enables the transmission of CD-quality audio. However, this requires a compatible Android device with a Qualcomm Snapdragon 888 or newer processor.

- aptX Adaptive: When the headphones are connected to a Snapdragon Sound certified device, the aptX Adaptive Bluetooth codec is automatically used to ensure the best sound quality, connection stability and latency.

- LE Audio: The headphones also support LE Audio, which may be useful in public spaces and venues in the future as more LE Audio transmitters become available.

According to my research, it's tricky with the Bose QuietComfort Ultra.
Theoretically, they also support aptX-Adaptive and aptX-Lossless.
However, this ONLY if the transmitter (smartphone) is "Snapdragon Sound" certified.

https://www.aptx.com/products...