The 5.1 kernel is not yet supported by the most recent DisplayLink driver release, but it is already supported in the devel branch of evdi (
https://github.com/DisplayLink/evdi) which we will be using in
future Linux driver release.
You can compile evdi from github manually and use it with the 5.1 DisplayLink driver, although you would need to extract installer components and modify the installer script to cope with it (i.e. so it doesn't attempt to build the bundled evdi tarball).
Cheers,
Michal