"Don't use [] around ranges in tr, it replaces literal square brackets."

acme.sh

@@ -573,7 +573,7 @@ _createkey() {
 _is_idn() {
   _is_idn_d="$1"
   _debug2 _is_idn_d "$_is_idn_d"
-  _idn_temp=$(printf "%s" "$_is_idn_d" | tr -d '[0-9]' | tr -d '[a-z]' | tr -d '[A-Z]' | tr -d '.,-')
+  _idn_temp=$(printf "%s" "$_is_idn_d" | tr -d '0-9' | tr -d 'a-z' | tr -d 'A-Z' | tr -d '.,-')
   _debug2 _idn_temp "$_idn_temp"
   [ "$_idn_temp" ]
 }