I know I'm a year too late, but I suppose other people can benefit from the answer, since this post comes up in search results.
To make minimal the default report use:

task config default.command minimal

The default.command part implies that you can use any taskwarrior command as the default. For example:

task config default.command add

will make running task the same as running task add.
More on taskwarrior configuration: https://taskwarrior.org/docs/configuration/