Check out Zkool or Zingo , I think they can both import private keys.
As far as Sprout goes, if it’s coming from the sprout pool it may need to go transparent and then shielded again because of the turnstile. I’m not 100% sure, @Autotunafish may know better.
There has been talks about retiring old pools, especially sprout since it had some bugs, but nothing concrete planned for the near future.