To install, run nikola theme -i oldfashioned
This theme used to be called 'default' in version 5 of Nikola.
Strangely, it was never the actual default theme in any released version ;-)
It's a traditional 2-column, right-sidebar theme, bootstrap-based.
Supports Bootswatch color/font schemes through the
nikola bootswatch_theme command.
You can report issues with this theme and request help via GitHub Issues (themes repository).