Fix timestamps for photos saved via whatsapp, to have them show up correctly in Google Photos. Enable backup of both of the Cleansapp folders in Google Photos.

fix_timestamps.sh

#! /usr/bin/sh

# For Whatsapp saved photos.
adb pull -a -z zstd /storage/emulated/0/Pictures/Whatsapp ./
cd Whatsapp
exiftool '-FileCreateDate<${Filename; s/IMG-([0-9]{4})([0-9]{2})([0-9]{2})-.*\.jpg/$1:$2:$3 12:00:00+5:30/}' '-Exif:DateTimeOriginal<${Filename; s/IMG-([0-9]{4})([0-9]{2})([0-9]{2})-.*\.jpg/$1:$2:$3 12:00:00+5:30/}' *.jpg
cd ..
mv Whatsapp Cleansapp
adb push -z zstd ./Cleansapp /storage/emulated/0/Pictures/
rm -r Cleansapp

# For Whatsapp Videos
adb shell
cd /storage/emulated/0/Movies/Whatsapp
for file in `ls`; do touch -amt "$(echo $file | cut -d '-' -f 2)1200" $file; done
cd ..
mv Whatsapp/* Cleansapp/

May want to change the exiftool command to use AllDates

exiftool -overwrite_original -r -P "-AllDates<FileModifyDate" "your/output/folder/ALL_PHOTOS/"