I want those new low-TDP Ryzens either as AM4 socketed or mounted in mini-ITX motherboards, but only the higher TDP desktop models seem to be available.
Lenovo just released the Thinkpad X13 (an AMD version of the X1) for the first time. It has a 10/25w TDP 44/46/4750U. I think the focus right now for the lower TDP chips is laptop computing because that's where you'll see the most improvement. I've been following the market for the past 9 or so months because I need a new machine and both Intel and AMD have taken that strategy. Look at the ASUS G14. A laptop that can nab 10h of battery life on a 76 watt x h battery because its workstation (H, not U) series processor is only pulling 10W. And it benches close to a desktop 10th gen i7 at full power. It's getting exciting.
AMD really are trying to get in the enterprise laptop segment, simply because that's where Intel has had a near-monopoly since the Pentium M.
So I know why I can't get a good mini-ITX board, but I still really want one :-)
As is, my best option for the living room NAS/HTPC turned out to be a J4105 board from ASRock. 10w TDP and apparently it can do 4 simultaneous GPU-accelerated 4K transcodes, which is pretty neat. Perhaps I'll upgrade to an AMD board at some point.