This is a feature request for Joomla! 4.
It would be great if anyone could implement a character counter beneath the field of the meta description.
Yes, the plugin is working in Joomla 4 - I've tried it with the Alpha 5:
But this is a reverse character counter with fixed values. I think a simple character counter is more useful, because Google and perhaps another search engines too change the max length of titles and meta descriptions from time to time.
Should be fairly simple to add, possible adjust the JForm fields to have a display count when limit is in force