Specifically for computers to smart speakers, I use AirPlay 1, but this works better from Windows with a 3rd-party app than from iOS or MacOS—the 3rd party app

Specifically for computers to smart speakers, I use AirPlay 1, but this works better from Windows with a 3rd-party app than from iOS or MacOS—the 3rd party app is perfectly happy to play to as many endpoints as I like, while Apple will only transmit to one endpoint at a time if it's an AirPlay 1 device. From my Windows 10 PC, TuneBlade AirPlay streaming provides a great experience: I can play stream anything that is playing on the PC to any AirPlay device on my LAN, and all the playback devices will be in perfect audio sync. AirPlay 1 devices on my network include an AppleTV, Apple HomePod Minis, Nexum Airplay receivers attached to powered speakers, and DAPs with Airplay reception. There is a significant buffer delay—about 2 seconds—that messes with video streaming. TuneBlade has the ability to stream video to VLC with synced audio, but doesn't support other video streaming endpoints. There is a bufferless mode with no delay, but it doesn't work well on my network.