A year or two later, and INSTALL.PHP is back in the /WP-ADMIN/ folder.

Is this normal? Is it added during WordPress version updates? Is there a way to prevent this file from being reloaded to the site?

https://www.mysite.com/wp-admin/install.php

And it DID give the Language Options menu. So it looked like it was trying to reinstall WordPress from scratch. Had me pretty scared that a user might create a new username / password & lock me out.

(I later learned that this happened while the database briefly went down on the server.)

At any rate, I’m now using an HTACCESS rule in the root directory to deny access to the install file:

##########################################################
### PREVENT ANYONE FROM RUNNING INSTALL.PHP IN /WP-ADMIN/
##########################################################
Options +FollowSymLinks
RewriteEngine On
RewriteRule ^/?wp-admin/install\.php$ - [F,L]