[Moto G Play (2021)] latentspork:
First time posting and I wanted to say thank you to all the excellent talent here on XDA! None of this would have been done without the work of so many people.

I have a Moto G Play (2021) (XT2093-4) that I recently purchased (Best Buy - $159 US/Carrier Unlocked) and I wanted to document my adventure in to rooting, making '/system' RW, and fixing the missing LED notification light (hint: I used the charging light) (hint^2: It's not required to make '/system' RW in order to fix the LED notification light - I just wanted more control over my phone).

First, "OEM unlocking" was greyed out for me, but became available after several days of having the phone online with a SIM card.

I followed the instructions here to unlock the bootloader and root with Magisk (Non-TWRP). Along with these instructions.

Once bootloader is unlocked, you will need the 'boot.img' file from your stock firmware. I used the "Rescue and Smart Assistant" utility to grab a copy of the stock firmware (GUAMNA_RETAIL_QZAS30.Q4_39_35_9_subsidy_DEFAULT_regulatory_DEFAULT_CFC.xml) and extracted the "boot.img" file for the next steps.

Continue installing Magisk (Filenames may be different! Don't just copy and paste.):

adb install Magisk-v23.0.apk
adb push boot.img /sdcard/Download
(Follow the instruction on your phone to patch 'boot.img' in Magisk)
adb pull /sdcard/Download/magisk_patched-23000_aKKMt.img
adb reboot bootloader
fastboot flash boot_a magisk_patched-23000_aKKMt.img
fastboot flash boot_b magisk_patched-23000_aKKMt.img

You should now have a working, rooted Moto G Play. You can just stop here and have fun with your phone, but I noticed that even with root, the system partition was not RW.

I followed these instructions to make '/system' writable (Note: you will need the 'sysrw_repair.zip' that's included in the bundle and a Linux system):

adb push systemrw_1.32_flashable.zip /data/local/tmp/
adb shell
su
cd /data/local/tmp/
unzip systemrw_1.32_flashable.zip
cd systemrw_1.32/
chmod +x systemrw.sh
./systemrw.sh in=`ls -l /dev/block/by-name/super | awk '{print $NF}'` out=/data/local/tmp/systemrw_1.32/img/super_original.bin size=50

The phone doesn't have enough space to complete 'lpmake' on the device and will end with an "Error 73" code. Running the "sysrw_repair_v1.32" tool on a Linux machine was a workaround because it pulls the '*.img" files to your local machine then combines them in to a single '.bin' file. But, before I did that, and because it's really annoying, I made some room to stop the phone from complaining about a lack of space:

(Still on the phone's adb)

rm ./img/super_original.bin

Now, on the Linux machine, I unzipped 'sysrw_repair_v1.32_proper.zip' then commented out line 39 (where it calls the "flash()" function) of the script (sysrw_repair.sh) because I wanted to flash the "super" partition myself.

(On another Linux terminal)

cd /path/to/unzipped/sysrw_repair/dir/
chmod +x sysrw_repair.sh
./sysrw_repair.sh

This results in a new folder (img) with a rather large bin file (super_original.bin).

(Back on the phone adb)

exit # Exit root
exit # Exit adb
adb reboot bootloader

Now it's time to flash the fixed bin file to the "super" partition:

cd /path/to/unzipped/sysrw_repair/dir/
fastboot flash super ./img/super_original.bin
fastboot reboot

You should be able to login and have a writable '/system':

adb shell
su
mount -o rw,remount /

No errors should appear.

Last, I like having an LED indicator that tells me that I have an SMS/MMS notification waiting. Motorola thought it would be wise to eliminate that feature altogether instead of having the option to enable it. So, I forced it back on using a startup script that dumps the notifications and greps for some key words. And, if it finds something, it "breaths" the charging LED. The script loops until the notification is gone, then keeps checking for new notifications every 30 seconds. (Note: the "/data/adb/service.d/" directory is used by Magisk like an INIT service):

(Still root on the phones adb)

cd /data/adb/service.d/
cat <<EOF > ledfix.sh
#!/bin/sh

while true; do
if dumpsys notification | egrep NotificationRecord | egrep sms > /dev/null
then
if [[ $(cat /sys/class/leds/charging/breath) == 0 ]]
then
echo 1 > /sys/class/leds/charging/breath
sleep 2
continue
else
sleep 2
continue
fi
elif egrep 'Charging' /sys/class/power_supply/battery/status > /dev/null
then
if [[ $(cat /sys/class/leds/charging/breath) -ne 0 && $(cat /sys/class/leds/charging/brightness) -ne 0 ]]
then
echo 0 > /sys/class/leds/charging/breath
echo 255 > /sys/class/leds/charging/brightness
elif [[ $(cat /sys/class/leds/charging/breath) == 0 && $(cat /sys/class/leds/charging/brightness) == 0 ]]
then
echo 255 > /sys/class/leds/charging/brightness
else
continue
fi
else
echo 0 > /sys/class/leds/charging/breath
echo 0 > /sys/class/leds/charging/brightness
fi
sleep 30
done
EOF
chown 0.0 ledfix.sh
chmod 0755 ledfix.sh
reboot

Now, the charging light will fade off and on about every 2 seconds if there's an SMS/MMS notification waiting. And will check for notifications every 30 seconds. I'm sure someone can come up with a better way of doing this, but this was a nice quick-and-dirty way to get what I wanted.

Hope this helps!