Discourse has many import scripts and among them there’s also a Google Groups one. Have you tried a test with it and see if you can bring the old content around? It would be helpful for many people instead of replying again to old questions and whatnot. Just thinking it might be a good idea. I put this here in the off topic section because i didn’t know where else it would fit.
We’re on a free tier for open source projects, and from what I read it’s not an option we can take advantage of. I suspect there could also be several issues, including (but not limited to) the lack of categorization on GG (we’d have to manually move ~5000 messages) and potential mismatches between participants there and here (I for one am registered with a different mail, for instance).
As such, I personally feel it’s better to just start fresh with a new environment: as time goes by, more and more topics will start appearing here too, providing useful info people can search. I don’t plan to completely destroy the GG anyway, which means it can stay there for historic reasons and as an archive of past discussions.
Please tell me this service can send a daily email?!?! 
From what I read it’s a thing you can configure in your preferences, somewhere in your profile settings.
