This seems like an oversight to me. 775 is DOS Baltic, 737 is DOS Greek. The DOS code pages are what get resolved on Linux when not set to UTF-8 everywhere, e.g. lt_LT. Seems to also affect Android?
Causes the issue described on https://forums.xamarin.com/discussion/61880/system-notsupportedexception-regarding-encoding
Additional issue caused by this bug:
Is it impossible to compile monodevelop from source.
Make command throws error:
The type initializer for 'PACKAGE_xxx' threw an exception.
No data is available for encoding 775.
Workaround is to set a different locale, for example C:
After that everything seems to be working.
Fixed with https://github.com/mono/mono/pull/6361