Hello
in the admin, i have a notification mentioning there are 3 overrides ( substitution in french ) to be verified. If i click on it , i get this, then you can click on the file and see what will be modified
Looks like what it says is that Joomla 4 modified the original files so the developpers should look at the way they are overriding on the flagged template files.
Comparing original files and the template files show differences
Maybe devs should have look at those files before a joomla update kills something