Manual:$wgMainPageIsDomainRoot

Server URLs and file paths: $wgMainPageIsDomainRoot
Controls if the main page should be served as the domain root.
Introduced in version:1.34.0 (Gerrit change 520139; git #a5deeac5)
Removed in version:still in use
Allowed values:(boolean)
Default value:false

If true, users visiting your wiki's main page from the domain root will not be redirected. This setting requires that short URLs be configured in order to be functional.

Setting this may incur in some overhead. See task T302186.