Can't get zigbee2mqtt onboarded in HA

yes, Mosquito is installed, locally.

data_path: /config/zigbee2mqtt
socat:
  enabled: false
  master: pty,raw,echo=0,link=/tmp/ttyZ2M,mode=777
  slave: tcp-listen:8485,keepalive,nodelay,reuseaddr,keepidle=1,keepintvl=1,keepcnt=5
  options: "-d -d"
  log: false
mqtt:
  server: mqtt://172.16.10.yy:1883
  user: pairs
  password: apples
  base_topic: homeassistant
serial:
  port: tcp://172.16.10.xx:6638
  adapter: zstack
  baudrate: 115200