I feel your pain 🙂
This suggestion above was my initial approach to moving from the default environment, but very few flows can be added to a solution if they are not in solutions already (the majority in my case).
I did think maybe you could export the default solution which contains everything (kind of) and reimport it, but that option is greyed out. This could be something MS support might be able to do, but in my previous support call, they said the only option is to manually move everything.
As an aside, not sure if you have noticed yet, but when a new Dataverse in Teams environment is fired up, it takes the default environment's region, another disaster in my case !
My approach was to make the app owners rebuild their apps inside solutions, but that had an uptake of none.
