Backup/restore private data of any debuggable app on Android without root (uses Shizuku)

.bashrc

run-as() {
  local escaped_args=()
  for arg in "$@"; do
    escaped_args+=("'${arg//\'/\'\\\'\'}'")
  done
  local IFS=' '
  rish -c "/system/bin/run-as ${escaped_args[*]}"
}

backup-app() {
  if [[ $# -ne 3 ]]; then
    echo "Backup an app to a .tar.gz file." >&2
    echo "usage: backup-app <package> <user> <file>" >&2
    return 1
  fi
  run-as "$1" --user "$2" /system/bin/tar -czvf - . > "$3" || return 1
  echo ">>> DONE"
}

restore-app() {
  if [[ $# -ne 3 ]]; then
    echo "Restore an app from a .tar.gz file. Replaces all existing app data." >&2
    echo "usage: restore-app <package> <user> <file>" >&2
    return 1
  fi
  echo ">>> Deleting existing app data:"
  run-as "$1" --user "$2" /system/bin/find -mindepth 1 -delete || return 1
  echo ">>> Restoring new app data:"
  run-as "$1" --user "$2" /system/bin/tar -xzvf - < "$3" || return 1
  echo ">>> DONE"
}