[LG V60 ThinQ Guides, News, & Discussion] athoz:
Did you get any solution with this? I am on the same boat T-Mobile unit. Did it brick after rebooting?

edit: Before rebooting I run again the ./systemrw.sh size=20 (first time was 15) and flashed it in bootloader. The device bricked when I made a reboot.

This second time in systemrw.sh the report had "systemrw: / is already R/W capable. Ignoring" so it seems that it is RW but I couldn't write the build.prop or make new folder using ES file explorer or adb shell mkdir.

timelm:/data/local/tmp/systemrw_1.32 # ./systemrw.sh size=20
--------------------------------------------------
| SystemRW v1.32 automated script by lebigmac |
| @xda ©2021 Big thank you to @Kolibass @Brepro1 |
|@munjeni @AndyYan @gabrielfrias @YOisuPU @bynarie |
| without your help this would not be possible! |
--------------------------------------------------

systemrw: Custom size detected: 20 MB
systemrw: Initiating procedure...

systemrw: Device is in Android mode. Ignoring
systemrw: Current device: LGE
systemrw: Current Android version: 12
systemrw: Current SELinux status: Permissive
systemrw: Current slot is: 1
systemrw: Your super partition is located at: /dev/block/sda25
systemrw: / is already R/W capable. Ignoring
systemrw: /product is read-only
systemrw: /vendor is already R/W capable. Ignoring
systemrw: Adjusting permissions...
systemrw: Attempting to disable dm-verity and verification...
verification is already disabled on slot with suffix _b.
verity is already disabled on slot with suffix _b.
systemrw: Dumping super partition to: /data/local/tmp/systemrw_1.32/img/super_original.bin
systemrw: Please wait patiently...

41943040+0 records in
41943040+0 records out
21474836480 bytes (20 G) copied, 148.569186 s, 138 M/s

systemrw: Successfully dumped super partition to: /data/local/tmp/systemrw_1.32/img/super_original.bin
systemrw: Unpacking embedded partitions from /data/local/tmp/systemrw_1.32/img/super_original.bin
systemrw: Nested partitions were successfully extracted from super

systemrw: Current size of product_a.img in bytes: 4180418560
systemrw: Current size of product_a.img in MB: 3986
systemrw: Current size of product_a.img in 512-byte sectors: 8164880

systemrw: NO 'shared_blocks feature' detected @ product_a.img

systemrw: Shrinking size of product_a.img back to minimum size...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/product_a.img to 1016771 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/product_a.img is now 1016771 (4k) blocks long.

systemrw: Custom size of product_a.img in bytes: 4185665536
systemrw: Custom size of product_a.img in MB: 3991
systemrw: Custom size of product_a.img in 512-byte sectors: 8175128

systemrw: Increasing filesystem size of product_a.img...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/product_a.img to 1021891 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/product_a.img is now 1021891 (4k) blocks long.

=================================================

systemrw: Current size of system_a.img in bytes: 2757193728
systemrw: Current size of system_a.img in MB: 2629
systemrw: Current size of system_a.img in 512-byte sectors: 5385144

systemrw: NO 'shared_blocks feature' detected @ system_a.img

systemrw: Shrinking size of system_a.img back to minimum size...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/system_a.img to 669306 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/system_a.img is now 669306 (4k) blocks long.

systemrw: Custom size of system_a.img in bytes: 2762448896
systemrw: Custom size of system_a.img in MB: 2634
systemrw: Custom size of system_a.img in 512-byte sectors: 5395408

systemrw: Increasing filesystem size of system_a.img...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/system_a.img to 674426 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/system_a.img is now 674426 (4k) blocks long.

=================================================

systemrw: Current size of vendor_a.img in bytes: 1464115200
systemrw: Current size of vendor_a.img in MB: 1396
systemrw: Current size of vendor_a.img in 512-byte sectors: 2859600

systemrw: NO 'shared_blocks feature' detected @ vendor_a.img

systemrw: Shrinking size of vendor_a.img back to minimum size...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/vendor_a.img to 353615 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/vendor_a.img is now 353615 (4k) blocks long.

systemrw: Custom size of vendor_a.img in bytes: 1469378560
systemrw: Custom size of vendor_a.img in MB: 1401
systemrw: Custom size of vendor_a.img in 512-byte sectors: 2869880

systemrw: Increasing filesystem size of vendor_a.img...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/vendor_a.img to 358735 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/vendor_a.img is now 358735 (4k) blocks long.

=================================================

systemrw: Current size of product_b.img in bytes: 4179726336
systemrw: Current size of product_b.img in MB: 3986
systemrw: Current size of product_b.img in 512-byte sectors: 8163528

systemrw: NO 'shared_blocks feature' detected @ product_b.img

systemrw: Shrinking size of product_b.img back to minimum size...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/product_b.img to 1016602 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/product_b.img is now 1016602 (4k) blocks long.

systemrw: Custom size of product_b.img in bytes: 4184973312
systemrw: Custom size of product_b.img in MB: 3991
systemrw: Custom size of product_b.img in 512-byte sectors: 8173776

systemrw: Increasing filesystem size of product_b.img...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/product_b.img to 1021722 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/product_b.img is now 1021722 (4k) blocks long.

=================================================

systemrw: Current size of system_b.img in bytes: 2757230592
systemrw: Current size of system_b.img in MB: 2629
systemrw: Current size of system_b.img in 512-byte sectors: 5385216

systemrw: NO 'shared_blocks feature' detected @ system_b.img

systemrw: Shrinking size of system_b.img back to minimum size...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/system_b.img to 669312 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/system_b.img is now 669312 (4k) blocks long.

systemrw: Custom size of system_b.img in bytes: 2762473472
systemrw: Custom size of system_b.img in MB: 2634
systemrw: Custom size of system_b.img in 512-byte sectors: 5395456

systemrw: Increasing filesystem size of system_b.img...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/system_b.img to 674432 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/system_b.img is now 674432 (4k) blocks long.

=================================================

systemrw: Current size of vendor_b.img in bytes: 1464115200
systemrw: Current size of vendor_b.img in MB: 1396
systemrw: Current size of vendor_b.img in 512-byte sectors: 2859600

systemrw: NO 'shared_blocks feature' detected @ vendor_b.img

systemrw: Shrinking size of vendor_b.img back to minimum size...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/vendor_b.img to 353615 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/vendor_b.img is now 353615 (4k) blocks long.

systemrw: Custom size of vendor_b.img in bytes: 1469378560
systemrw: Custom size of vendor_b.img in MB: 1401
systemrw: Custom size of vendor_b.img in 512-byte sectors: 2869880

systemrw: Increasing filesystem size of vendor_b.img...
resize2fs 1.45.4 (23-Sep-2019)
Resizing the filesystem on /data/local/tmp/systemrw_1.32/img/vendor_b.img to 358735 (4k) blocks.
The filesystem on /data/local/tmp/systemrw_1.32/img/vendor_b.img is now 358735 (4k) blocks long.

=================================================

systemrw: Joining all extracted images back into one single super image...
systemrw: Please wait and ignore the invalid sparse warnings...

Invalid sparse file format at header magic
Invalid sparse file format at header magic
Invalid sparse file format at header magic
Invalid sparse file format at header magic
Invalid sparse file format at header magic
Invalid sparse file format at header magic

systemrw: Successfully created patched super image @
systemrw: /data/local/tmp/systemrw_1.32/img/super_fixed.bin

systemrw: Congratulations! Your image(s) should now have R/W capability
systemrw: Please reboot into bootloader and flash the file(s) manually

and the flashing report looks good as well.

PS D:\v60\original\systemrw\img> fastboot flash super .\super_fixed.bin
Sending sparse 'super' 1/21 (784564 KB) OKAY [ 27.436s]
Writing 'super' OKAY [ 8.367s]
Sending sparse 'super' 2/21 (784479 KB) OKAY [ 29.226s]
Writing 'super' OKAY [ 4.781s]
Sending sparse 'super' 3/21 (784540 KB) OKAY [ 29.417s]
Writing 'super' OKAY [ 7.222s]
Sending sparse 'super' 4/21 (785793 KB) OKAY [ 28.705s]
Writing 'super' OKAY [ 8.454s]
Sending sparse 'super' 5/21 (786420 KB) OKAY [ 29.642s]
Writing 'super' OKAY [ 9.291s]
Sending sparse 'super' 6/21 (778317 KB) OKAY [ 29.327s]
Writing 'super' OKAY [ 9.877s]
Sending sparse 'super' 7/21 (782081 KB) OKAY [ 29.342s]
Writing 'super' OKAY [ 7.783s]
Sending sparse 'super' 8/21 (784999 KB) OKAY [ 29.064s]
Writing 'super' OKAY [ 8.455s]
Sending sparse 'super' 9/21 (778698 KB) OKAY [ 29.023s]
Writing 'super' OKAY [ 8.579s]
Sending sparse 'super' 10/21 (770578 KB) OKAY [ 28.579s]
Writing 'super' OKAY [ 6.618s]
Sending sparse 'super' 11/21 (762903 KB) OKAY [ 28.582s]
Writing 'super' OKAY [ 5.970s]
Sending sparse 'super' 12/21 (744945 KB) OKAY [ 27.756s]
Writing 'super' OKAY [ 8.503s]
Sending sparse 'super' 13/21 (776741 KB) OKAY [ 29.118s]
Writing 'super' OKAY [ 8.862s]
Sending sparse 'super' 14/21 (772049 KB) OKAY [ 28.644s]
Writing 'super' OKAY [ 5.171s]
Sending sparse 'super' 15/21 (779378 KB) OKAY [ 28.746s]
Writing 'super' OKAY [ 5.953s]
Sending sparse 'super' 16/21 (783456 KB) OKAY [ 29.425s]
Writing 'super' OKAY [ 7.568s]
Sending sparse 'super' 17/21 (780745 KB) OKAY [ 28.948s]
Writing 'super' OKAY [ 8.619s]
Sending sparse 'super' 18/21 (784360 KB) OKAY [ 29.501s]
Writing 'super' OKAY [ 9.608s]
Sending sparse 'super' 19/21 (781426 KB) OKAY [ 29.460s]
Writing 'super' OKAY [ 8.857s]
Sending sparse 'super' 20/21 (783530 KB) OKAY [ 29.506s]
Writing 'super' OKAY [ 9.723s]
Sending sparse 'super' 21/21 (678409 KB) OKAY [ 25.383s]
Writing 'super' OKAY [ 7.932s]
Finished. Total time: 779.232s

Is there any suggestion before I try to start from scratch? Should I refurbish in LGUP the last firmware or restore the backup from QFIL?

Cheers!