RG520N - read-only file system

Hallo,
I am trying to install some utilities on the module, but I get errors like
cp: cannot create regular file `/lib/systemd/system/socat-killsmd7bridge.service’: Read-only file system

Tried the solution propsed in another post:

and also
mount -o remount,rw /
but without results.
Is there any way to make the file system writable ?
Thanks in advance

What’s firmware version?
Please check with AT command
AT+QGMR

For standard firmware, you might not have the access to modify the filesystem.
You can put some files in /usr/ folder.

Firmware version is RG520NEUDBR01A06M8GA.

Is there any other firmware available with write access ?
If yes could you please send it ?
Thanks

It is not opensolution. So you don’t have the access to modiy the filesystem.
Can you push files into /usr/?