Playing BBC Radio 4 on Sonos with Google Assistant in Canada

If you want to use Google Assistant to play BBC Radio 4 in Canada on a Sonos (as of Nov 10, 2022)...

"Hey Google, play BBC Radio 4"

It won't work.  It will play BBC Radio 4 Extra (a completely different channel) from TuneIn.

You might say, well, maybe it's a problem with TuneIn, I'll get Google Assistant to play it from Sonos Radio.

It won't work.  Google Assistant can't play anything from Sonos Radio.

You might say, well fine, I'll use Sonos Voice Control for this edge case.

You must disable Google Assistant for Sonos Voice Control to work (inexplicably, since clearly the system should be able to route requests for "Hey Google" and "Hey Sonos" to different targets).  So unless you want to disable Google Assistant, it won't work.

This may seem like an edge case, but it's an outstanding request that hasn't been resolved for a year.  See for example this extensive thread:

https://en.community.sonos.com/google%2Dassistant%2Dand%2Dsonos%2D229109/radio%2D4%2Dvoice%2Dcommand%2Dstopped%2Dworking%2D6859212?postid=16541128#post16541128

NOTE: This has nothing to do with BBC Sounds, that's a UK-specific issue.

BBC Radio 4 is absolutely on TuneIn in Canada.  It is also on Sonos Radio, for whatever use that is.