Easy enough in fheory, add a crossover.

Picking the right crossover is the trick.

There is plenty of info from people who have done it the opposite way with Ikea Symfonisk.

Attach the Sonos board to different speaker drivers because the board is held back by the small drivers and bypassing the crossover in passive speakers is trivial.

As @Stanley_4 says the opposite way is easy enough in theory. Remove the Sonos board and insert a crossover.

One unusual thing that came out of people disassembling the Symfonisk is the crossover point used by Sonos is low in comparison to many speakers.

Measurements I’ve seen put it at ~1.4Khz so unless you get lucky or can design an appropriate crossover depending on the Play1 driver frequency responses, you likely get better and easier results with a digital processor feeding an amp per driver.