Setting a sleep timer for radio on Sonos with Google Assistant

If you want to use Google Assistant to set a sleep timer in Canada on a Sonos (as of Nov 10, 2022) while playing radio (e.g. a TuneIn station)...

"Hey Google, set a sleep timer for twenty minutes"

It won't work.  It will say:

Sleep timers can only be set when media is playing.

Even though media is in fact actually playing.

This is a known issue that has been outstanding now for three years.

https://en.community.sonos.com/google-assistant-and-sonos-229109/sleep-timer-doesn-t-work-with-google-assistant-6825551