Ubuntu 18.04.2 LTS with A 5.1.9 KERNEL

[emilie]

I eventually managed to compile and install (I will explain what I did just in case someone has the same problem than me)
So far so good: DisplayLink seems to work good for me on Ubuntu 18.04 with a 5.1.9 kernel and 2 screens plugged on a amazon dock

I did

./displaylink-driver-5.1.26.run --noexec --keep
cd displaylink-driver-5.1.26
sudo displaylink-installer.sh install

it failed with the error I pasted ahead
then I downloaded evdi v1.6.1 on https://github.com/DisplayLink/evdi/releases since it has support for 5.0 and 5.1 kernels
rm the content of /usr/src/evdi-5.1.26
unzipped evdi-1.6.1.zip and copied evdi-1.6.1/module/* in /usr/src/evdi-5.1.26
retried

sudo displaylink-installer.sh install 
reboot

/!\ there must be a less dirty way than replace code