It seems that with v278 it is a little bit better. Now save and load windows always show up, saving seems to work (savefiles are created), but opening a load window is buggy - there is a save on a list but without any information about it and you cannot load it.
The problem is due to this Mono exception:
Seems that the savegame is visible for the game so only unzipping of the savegame does not work.
I can already see that some other bugs that were present were fixed, but this is still (probably the only) one that prevents anyone on Linux from playing.