How do gamboostLSS and gamlss packages predict outside range of x?

The mgcv package performs a linear extrapolation when the newdat argument of the predict function contains values outside the range of the training covariates. I am unable to find out what happens in this use case for the gamboostLSS package and the gamlss and mboost packages on which it is based.

We had an email exchange in 2015 and decided to use linear extrapolation for smooth effects (both, P-splines and constraint P-splines). This was implemented in mboost 2.5-0. See news(Version >= "2.5-0", package = "mboost") and package?mboost for more details.