I switched away from my Microsoft Designer keyboard/mouse combo because the keyboard wouldn't retain it's Bluetooth connection to my PC on reboots, therefore signing in became a serious hassle & re-pairing every time rapidly became boring. Honestly, who wants a wired USB keyboard on hand for the first few minutes after restarting your PC? Not me.
Microsoft's advice is that they accept that the Bluetooth connection breaks from onboard receivers because of a hardware issue & that I should purchase a separate USB Bluetooth dongle to enable continued connection. Really? You know where you can stick that advice, don't you? My USB ports are full & I expect that a product from Microsoft will work out of the box. Unless it's Kin but let's not go there.
So I swapped my Apple Magic keyboard from my Sony Android TV to the PC - no drama there & it retains the connection. It's only a mini keyboard though, I chose the Microsoft particularly because it's a full size keyboard.
Pairing the Microsoft Designer keyboard to the TV OMG - immediate recognition, acceptance then rejection. Try, try, try again, nope, not even. The packaging says it's compatible with Android TV but an online check shows small print detail making that statement so close to a lie - compatible with up to Android 5. Are there any Android 5 devices left? This keyboard is a new product, it wasn't even invented when Lollipop was superceded. This keyboard is obviously not made by the Surface team.
The unbelievable arrogance of the MS responders to people questioning why their $200 MS Designer keyboard won't connect to Android televisions was shocking - along the lines of "Can't you read? It says plainly up to Lollipop & you're trying to connect to Pie. PEBKAC error". I lost a lot of respect for Microsoft that day - the hardware is sub consumer guarantees level & the service responders were lucky that I don't know where they live.
I don't know the finer points of Android / Bluetooth integration, I always thought the Bluetooth protocol was independent of OS - a Bluetooth 4 controller should connect to a Bluetooth 4 receiver, unless artificially limited like iPhones do. I've never had a Bluetooth device fail to connect like this before.
The Bluetooth radio in the keyboard was clearly the cheapest one available & very limited in ability. I'm thinking that they didn't test it on Windows reboots before release & made the brave assumption that owners wouldn't be connecting MS gear to Android devices. Wrong. The pinheads on this product team need to get outside more often.
The Microsoft Designer keyboard is nicely finished & feels good to use. I don't like the shape of the Designer mouse & never used it, preferring my Logitech mouses. All good on the outside (except it's black - every speck of dust & dirt is obvious), but the internals have a serious hardware deficiency that can't be software patched. For this reason, the Microsoft Designer keyboard is unfit for purpose.
Don't buy one. Ever.