Unable to modify /system/etc/permissions/platform.xml

I have a rooted Galaxy S5 SM-G900V, lineage_klte, ARMv7 Processor rev 1 (v71), Kernel: 3.4.113-lineageos #1 SMP, Oreo 8.1

I need to modify the platform.xml file to allow system to write data to my external sd card. In particular Jota Text editor needs access to external sd card. The dir’s and file are read only. I was able to change /system and /etc to RW using ‘mount -o rw,remount /system’ then ‘chmod 777 /system’ and ‘chmod 777 /system/etc’. When I changed into the /etc dir and then tried to ‘chmod 777 /permissions’ I got the error ‘chmod: /permissions: No such file or directory’

After several hours of research I came to the conclusion that the dir’s /etc and /permissions and the *.xml file had their attribute set to “immutable”. I then downloaded toybox-armv7m, renamed to toybox, pushed to ‘/data/local/tmp/’ then ‘chmod 755 /data/local/tmp/toybox’. After verifying it worked I used ‘lsattr’ to get the attribues.

Unfortunately the result (for both dir’s and file) was ‘——-A—–‘ so no ‘i’ immutable attribute – shucks!

My question is how to make the sd card work as it did in my old s3? I do not want to make it adoptable! Any help is most appreciated!