Tag view gives 404
From Joomla! Documentation
In some websites, updating to Joomla 3.9.17 results in the tags view giving a 404.
This pertains only to Joomla! version(s): 3.9.17
What is the cause
An issue was missed whilst testing a performance improvement that only affected the tag view
How to fix
Update to Joomla 3.9.18. In the meantime you can apply the code change here to the components/com_tags/models/tag.php file