tests/bluetooth/tester/nrf5340_hci_ipc.conf

# Apply this overlay at tester build, not hci_ipc build
CONFIG_BT_MAX_CONN=3
# Those have to be the same as in the controller (hci_ipc)
CONFIG_BT_BUF_EVT_RX_COUNT=16
CONFIG_BT_BUF_EVT_RX_SIZE=255
CONFIG_BT_BUF_CMD_TX_SIZE=255