There is a well reported bug since a Joomla upgrade where logging in on the frontpage causes redirection to com_users/profile.

This has been addressed successfully in this thread

However, the thread mentions making a change to modules/mod_community_toolbar

Presumably, to address a redirection problem on logout from the logout icon on the toolbar menu? (this is only a guess of mine...)

Now, my problem is, I cannot locate mod_community_toolbar anywhere in my file structure. It is certainly not present under root/modules.

Many thanks for your help.

best wishes,
Mark

Hi, Mark.

It's because you don't use Socialize template. mod_community_toolbar is part of template package.
But you still may fix your issue by enabling and configuring JomSocial Redirect plugin.
You don't have to do anything in code.
Just set menu item to redirect after login, logout and failed login.
You have this plugin for sure as it's part of JomSocial package.