If anyone is on the same boat here's the best non-smart/IoT/lock-in tech I've come up with for a single room setup with wireless speakers:
1) 4 to 1 HDMI splitter with audio out: https://www.aliexpress.com/item/HDSW4-HDMI-Switch-4X1-With-A...
2) Connect all your sources through HDMI (your PC, your TV box, a Chromecast, a raspberry, etc). There are versions with more inputs if you need that. That one has a nice simple remote.
3) Connect the HDMI splitter audio output to a RF audio transmitter: https://www.altoproaudio.com/products/stealth-wireless
4) Use some powered studio monitors with one of the RF receivers each (there are plenty to choose from)
This way if you're streaming audio+video everything syncs up because the RF link adds very little latency (unlike the Sonos that adds 70ms). The chromecast gives you easy streaming of audio and video from all your apps and if you are only streaming audio you can just turn off your TV/projector and the audio still works fine. The speakers can be placed anywhere there's power. It doesn't have the fancy multi-room and 5.1 possibilities of the Sonos nor the good industrial design.