Thanks for the bug report.
Based on your description, the only thing I can think of is network access. When the game starts and after completing each level, a request is send to the server which keeps track of the results. Unfortunately, I haven't managed to make this request asynchronously on linux, that's why it might take a long time. But 3 to 5 mins is excessive. The most I've observed is about 30 secs during development when connecting to a local server which isn't running (so all requests timeout).
I'll try to fix that in the next update. Sorry for the inconvenience. Waiting that long to play for a couple of minutes must be really frustrating.