I am currently looking for a multiroom speaker system which does not force me to place wiretap into my home. Also it should be able to simultaneously play the same song on multiple speakers. Which device can you recommend me?
Best would be if no additional internet connection is necessary.
Sonos is probably the easiest one as others have mentioned. A bunch of raspberry pi’s with pulseaudio configured for remote streaming from a master audio source could also work for playing the same song in multiple locations if you want a more diy approach
Admittedly, I just use Sonos myself. However, I do hope to one day move to something else more open.
BluOS is another solution to look at. It's still pricey, but works offline and higher quality than Sonos if you're someone who has lots of high res music files.
Can't vouch for it, but looks interesting and according to the GitHub is still being updated so worth a look if you don't mind putting in some work and tinkering.