- Update to version 21.0
* New help viewer implementation, which includes DocBook files
in the resources. This avoids using an external browser, which
did not work with all installation directories on Ubuntu 21.10
because Firefox and Chromium have restricted access to local
files, or using WebView, which is not supported on all Linux
architectures or in Qt 6.0/6.1.
* Fixed visibility of labels on Callisto 1x1-piece in dark theme.
* Fixed rendering issues on Android with Qt 6.3.0.
* Fixed detection of loaded files or autosaved games modified by
another application.