Flutter is pretty nice, but I have a really hard time trusting Google to continue supporting it.

One of the Flutter primary devs just left Google and is still working on Flutter at his new gig.

That's a good sign that it's getting some momentum outside fo Google.

(I agree with you, though. Sadly, the Flutter management team seems to be where Google sends shitty managers for punishment.)

Is it https://shorebird.dev?

Does anyone use that in production for large B2C applications?

https://flutter.dev/showcase has many high profile examples

Yeah this answers the question pretty much

The French railway ticket website, sncf-connect.com is in Flutter.

Largest e-commerce service in France.

Google pay is written in Flutter