Hi… flyio/postgres is indeed officially deprecated now, as are all other self-managed Postgres images—along with all of the flyctl postgres commands:
Unmanaged Fly Postgres is deprecated in favor of ‘fly mpg’ (Managed Postgres). Please visit https://fly.io/docs/mpg/overview/ for more information about Managed Postgres.
This hasn’t fallen off a cliff yet, but you can generally expect a less and less smooth ride with Legacy Postgres as time goes on.
(I don’t speak for Fly.io in any way, though.)
There are some tips and caveats in this earlier thread, which might serve as a reference point…
(Not all of those apply to PG 14.)
Hope this helps a little!