Regarding flac support outside of a PC , both Sonos and squeezbox support flac
Logitech UK - Squeezebox Sonos Play:5 Wireless HiFi Player
Pretty much every standalone streamer that Ive come across plays the format too , such as Popcorn hour , WDTV , ACryan , and so on.
Some BD players also play the format.
For Apple devices , Apple via itunes have ALAC or the Apple Lossless Audio Codec , so dont support flac natively , rather they support their own proprietary codec , however , there are plenty of third party apps for all the apple devices that will happily play flac material.
I have an iphone 4 , an ipad , and a mac mini , all very capable of playing flac material through third party apps.
HDtracks supply music in flac format , I mention this one because its currently my favourite site to buy from , but there are plenty of others.
https://www.hdtracks.com/index.php?file=best_sellers
The best thing about flac in my opinion is that it is open source , so its encoders and tools are free , and will most likely be available indefinitely , so for encoding your collection for a home streaming system , this is by far the best way to go as it wont tie you to any particular manufacturer.
Once encoded in flac , the material is very flexible , in that in can be decompressed and re-compressed into any format you like. Flac is an excellent choice for your original material. As an Archive storage format , it is hard to beat.