set things under /data/adb/services.d/ and make them executable
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mount -o remount,rw / # then you can modify /sytem/etc/init.d, but not /system/bin cause it is a copy of /data/system/bin. you should create script there.
create this under /system/etc/init.d/
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service adb_wifi_enable /system/bin/adb_wifi_enable.sh disabled oneshot seclabel u:r:magisk:s0 on property:sys.boot_completed=1 start adb_wifi_enable