Kimsufi KS1 Server - Docker-ce installation error [fixed]

cyanogenic

EDIT: Fixed it, the KS1 came with a custom OVH kernel. I updated it to version 5.3 and was able to finish the installation.

I've got a Kimsufi KS-1 server. I put Ubuntu 16.04 on it and proceeded to upgrade to 18.04.
I tried to install docker by following the Digital Ocean guide.

I'm getting an error when trying to do the sudo apt install part of the guide. I've tried to google the errors down below but I'm not coming up with anything actionable. Just wondering if anyone could have a look and advice?

(Side note, I followed the guide on an Aruba VPS at the same time, fresh install of Ubuntu 18.04 and installed Docker no problem...)

root@Kimsufi:/# sudo apt install docker-ce docker-ce-cli
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
aufs-tools cgroupfs-mount libltdl7 pigz
The following NEW packages will be installed:
aufs-tools cgroupfs-mount docker-ce docker-ce-cli libltdl7 pigz
0 upgraded, 6 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/65.6 MB of archives.
After this operation, 293 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Selecting previously unselected package pigz.
(Reading database ... 77077 files and directories currently installed.)
Preparing to unpack .../0-pigz_2.4-1_amd64.deb ...
Unpacking pigz (2.4-1) ...
Selecting previously unselected package aufs-tools.
Preparing to unpack .../1-aufs-tools_1%3a4.9+20170918-1ubuntu1_amd64.deb ...
Unpacking aufs-tools (1:4.9+20170918-1ubuntu1) ...
Selecting previously unselected package cgroupfs-mount.
Preparing to unpack .../2-cgroupfs-mount_1.4_all.deb ...
Unpacking cgroupfs-mount (1.4) ...
Selecting previously unselected package docker-ce-cli.
Preparing to unpack .../3-docker-ce-cli_5%3a19.03.8~3-0~ubuntu-bionic_amd64.deb ...
Unpacking docker-ce-cli (5:19.03.8~3-0~ubuntu-bionic) ...
Selecting previously unselected package docker-ce.
Preparing to unpack .../4-docker-ce_5%3a19.03.8~3-0~ubuntu-bionic_amd64.deb ...
Unpacking docker-ce (5:19.03.8~3-0~ubuntu-bionic) ...
Selecting previously unselected package libltdl7:amd64.
Preparing to unpack .../5-libltdl7_2.4.6-2_amd64.deb ...
Unpacking libltdl7:amd64 (2.4.6-2) ...
Setting up aufs-tools (1:4.9+20170918-1ubuntu1) ...
Setting up cgroupfs-mount (1.4) ...
Setting up libltdl7:amd64 (2.4.6-2) ...
Setting up docker-ce-cli (5:19.03.8~3-0~ubuntu-bionic) ...
Setting up pigz (2.4-1) ...
Setting up docker-ce (5:19.03.8~3-0~ubuntu-bionic) ...
Created symlink /etc/systemd/system/multi-user.target.wants/docker.service → /lib/systemd/system/docker.service.
Created symlink /etc/systemd/system/sockets.target.wants/docker.socket → /lib/systemd/system/docker.socket.
Job for docker.service failed because the control process exited with error code.
See "systemctl status docker.service" and "journalctl -xe" for details.
invoke-rc.d: initscript docker, action "start" failed.
● docker.service - Docker Application Container Engine
Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/docker.service.d
└─cloudron.conf
Active: activating (auto-restart) (Result: exit-code) since Sun 2020-05-10 12:37:00 BST; 28ms ago
Docs: https://docs.docker.com
Process: 14619 ExecStart=/usr/bin/dockerd -H fd:// --log-driver=journald --exec-opt native.cgroupdriver=cgroupfs --storage-driver=overlay2 (code=exited, status=1/FAILURE)
Main PID: 14619 (code=exited, status=1/FAILURE)
dpkg: error processing package docker-ce (--configure):
installed docker-ce package post-installation script subprocess returned error exit status 1
Processing triggers for libc-bin (2.27-3ubuntu1) ...
Processing triggers for systemd (237-3ubuntu10.39) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for ureadahead (0.100.0-21) ...
Errors were encountered while processing:
docker-ce
E: Sub-process /usr/bin/dpkg returned an error code (1)