Facebook desktop app works reasonably well and supports many of the newer features, including live video. It makes using FB on a Win 10 tablet a nice experience.
Facebook on Win 10 Mobile though is an utter disaster. I should have kept the MS app as I had to uninstall it to try the FB version and now can't get the MS version back. The release FB app now requires 2GB ram which my 640 doesn't have (2GB, WTF!). The beta app runs about 1 time out of 100 and then crashes a minute later anyway. Utter total useless garbage.
FB though don't care. Windows Mobile is dead to them. They've done the minimal they could at the time to chuck an app out by using a terrible iOS wrapper, and that's it.
Microsoft don't care. Windows Mobile is also dead to them, except for their development teams who still cling on to the dream of run everywhere universal apps and a single OS. Development tools like Visual Studio still get a fair bit of love for this, but no new hardware to encourage developers. Surface Phone is a fantasy. 2019 at earliest now and frankly, it will never happen, or if it does, it will be a financial disaster like buying Nokia. The ship has long since sailed there. They know this which is also why the development teams of Microsoft are churning out a lot of cross platform tools to develop on iOS and Android.
Anyway, as a long time Nokia fan I've got my eye on the new Android Nokia releases. It's still not proper Nokia, but the Win Phones weren't either. Still, remnants of the old Nokia teams are behind it. Just hope they can do something a bit special with Android and not just be a generic Android in a device with Nokia's name on it.