Change mount attribute, but how?

I'm on Automotive Grade Linux. My system has a partition /dev/sda15 which is mounted to /data. I want to change the mount attribute "noexec" permanently, but 1. There is no directive for sda15 in /etc/fstab. 2. There is no corresponding systemd service in /etc/systemd/system. 3. GPT auto mounter is off by kernel parameter systemd.gpt_auto=0. How can I find the subsystem which mounts the partition? Kernel console does not mention sda15, UUID, PARTUUID or PARTLABEL. Journald is not indicating anything here. Remounting manually works (mount -o remount,exec /data) but is obviously not persistent. Adding an explicit entry in fstab does not work, after reboot, sda15 is still mounted noexec.