During the test run of Needlefish M1 the newer 5.15 kernels are unable to pair over bluetooth with a phone. Older 5.10 kernels on h3ulcb-kf and h3uclb-refhw pair properly and stream audio over bluetooth. There are no errors either in bluetooth journal other than timeouts.
The hardware is Logilink BT015 USB dongle with CSR 4.0 chipset which was used for testing in the last 3 years.
For comparison, RaspberryPi4 is able to pair with the onboard bcm bt running on 5.15.
There are a couple of threads that seem to have relevant information: