Out of the box, my Unifi Security Gateway runs Debian, as did my previous Unifi AC access points.

I just checked and my new Wifi 7 APs don't run Debian though, they...

    admin@BedroomAP:~# cat /etc/os-release
    NAME="OpenWrt"
    VERSION="23.05-SNAPSHOT"
    ID="openwrt"
    ID_LIKE="lede openwrt"
    PRETTY_NAME="OpenWrt 23.05-SNAPSHOT"
    VERSION_ID="23.05-snapshot"
    ....