Any way to play my own music uploaded to Google library?

Does a playlist containing your music work i wonder?

Does a playlist containing your music work i wonder?
If not, you could use IFTTT and the trigger to play a Sonos Favourite which can be locally stored.

It does work with playlists containing uploaded music, at least with the "Thumbs Up" playlist I have tried.

Unfortunately when I say "OK Google Shuffle My Thumbs Up Playlist" the tracks are not shuffled and it plays the same tracks in the same order every time - really poor!!!

I agree that these rules are a huge disappointment. Using Google Assistant to access my library on Google Play Music was the key feature I was looking for. It seems increasingly clear that the implementation of Google Assistant on Sonos falls far short of Google’s own speakers. Time to give Alexa a try.
I would've agreed with you, except that I already have Alexa and it's no better ... To make things worse with Alexa, she's really not smart and doesn't understand half the time or misunderstands the request

It does work with playlists containing uploaded music, at least with the "Thumbs Up" playlist I have tried.

Unfortunately when I say "OK Google Shuffle My Thumbs Up Playlist" the tracks are not shuffled and it plays the same tracks in the same order every time - really poor!!!

Go to olisto.com, create an account, link to Google Assistant service and Sonos service.

Create a "trigg" (automation routine) that sets your Sonos to shuffle play mode when you say to Google Assistant "set Sonos shuffle mode". Then play your playlist.

Interesting. Can you test playing just a single song, album, or artist, not a playlist and let me know if that works?

Unfortunately there is no way I know of to play a specific song/album/artist/playlist from your Sonos library using Google Assistant or Alexa. Obviously that's a gigantic shortcoming that Sonos has failed to address. The only thing you can do is play a specific Sonos Favorite, and you have to create a custom GA command for each favorite since Sonos hasn't bothered to support variable values in their IFTTT implementation.

Sonos has no control over the subscription requirements, they are set by the music services. Best to direct your anger over at Google Play Music.

feels like something for Sonos to solve though rather than Google, as I can play my music with no paid subscription from the app (so sonos can work with a free google play music subscription) and I can control it when it's playing via voice (so google assistant can control my music player), the two are just not completely joined up. Sounds like it can be fixed. Combine it with https://en.community.sonos.com/google-assistant-and-sonos-229109/any-way-to-play-my-own-music-uploaded-to-google-library-6825554?postid=16349451 which says "even with a subscription it doesn't work" and it says something's accidentally broken, rather than contractually disabled.