Here's the sorry state when trying to log into the official Facebook client for Windows Phone 8.1:
OK, so the next step is to take advantage of Facebook being largely web-based and to use the browser, right? So into Internet Explorer it is:
Which all looks OK, except that.... you can tap on ANY of the top controls. Facebook sections/messenger/menu/search, all are non-active. I suspect that it's something to do with the CSS and Javascript used by Facebook these days and lack of compatibility with Internet Explorer.
Next up were some of the Facebook 'clients' for WP8.1 - the one that looked most promising was Pages Manager. Skip past the bogus 'update available' dialog (it goes nowhere) and then it eventually errors out trying to authenticate with Facebook (stop me if this is sounding familiar!)
OK, last chance saloon. What about a third party browser that's more up to date than Internet Explorer?
I downloaded (from the Store) UC Browser and I was in luck, since this is more standards compliant. As a result, I can log into Facebook and use all its tabs and functions. Phew!
Now, obviously, this is subject to less screen real estate because there's a URL bar involved and there's 'full screen' as an option in UC Browser's Settings, so feel free to fiddle. But all the Facebook tabs and menu work just fine.
Phew! Any other Facebook solutions that work for ye olde Windows Phone 8.1 still? Comments welcome!