Udev rule to connect USB to CAN Lawicell

I am using a Lawicel CAN adapter to connect to a sensor, and would like to setup a udev rule to avoid the manual can setup. The manual can setup:

sudo slcand -o -c -f -s6 /dev/ttyUSB0 slcan0
sudo ifconfig slcan0 up

Running candump slcan0 shows, by printing data, that the connection works. I am thus following a guide to setting up the udev rule from [link](http://pascal-walter.blogspot.com/2015/08/installing-lawicel-canusb-on-linux.html) . But this doesn't work. The udev rule is

# Lawicel CANUSB module
ACTION=="add", ENV{ID_MODEL}=="CANUSB", ENV{SUBSYSTEM}=="tty", RUN+="/usr/bin/logger [udev] Lawicel CANUSB detected - running slcan_add.sh!", RUN+="/usr/local/bin/slcan_add.sh $kernel"
ACTION=="remove", ENV{ID_MODEL}=="CANUSB", ENV{SUBSYSTEM}=="usb", RUN+="/usr/bin/logger [udev] Lawicel CANUSB removed - running slcan_remove.sh!", RUN+="/usr/local/bin/slcan_remove.sh"

and the slcan_add.sh script is

#!/bin/sh
# Bind the USBCAN device
slcand -o -c -f -s6 /dev/$1 slcan0
sleep 2
ifconfig slcan0 up

then I reload the rules and restart udev, and tail -f /var/log/syslog returns the following

morten@thinkpad:~$ tail -f /var/log/syslog
Oct  7 10:56:21 thinkpad kernel: [ 1580.917239] usb 1-1: Detected FT232RL
Oct  7 10:56:21 thinkpad kernel: [ 1580.918002] usb 1-1: FTDI USB Serial Device converter now attached to ttyUSB0
Oct  7 10:56:21 thinkpad mtp-probe: checking bus 1, device 10: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-1"
Oct  7 10:56:21 thinkpad mtp-probe: bus: 1, device: 10 was not an MTP device
Oct  7 10:56:21 thinkpad root: [udev] Lawicel CANUSB detected - running slcan_add.sh!
Oct  7 10:56:21 thinkpad slcand: starting on TTY device /dev/ttyUSB0
Oct  7 10:56:21 thinkpad slcand: attached TTY /dev/ttyUSB0 to netdevice slcan0
Oct  7 10:56:21 thinkpad slcand: netdevice slcan0 renamed to slcan0
Oct  7 10:56:21 thinkpad NetworkManager:   [1633596981.6497] manager: (slcan0): new Generic device (/org/freedesktop/NetworkManager/Devices/8)
Oct  7 10:56:21 thinkpad systemd-udevd: ethtool: autonegotiation is unset or enabled, the speed and duplex are not writable.
Oct  7 10:56:23 thinkpad snapd: hotplug.go:199: hotplug device add event ignored, enable experimental.hotplug
Oct  7 10:56:23 thinkpad mtp-probe: checking bus 1, device 10: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-1"
Oct  7 10:56:23 thinkpad mtp-probe: bus: 1, device: 10 was not an MTP device
Oct  7 10:56:26 thinkpad ModemManager:   [base-manager] couldn't check support for device '/sys/devices/pci0000:00/0000:00:14.0/usb1/1-1': not supported by any plugin
Oct  7 10:56:27 thinkpad gnome-shell: Removing a network device that was not added
Oct  7 10:56:27 thinkpad gnome-shell: Removing a network device that was not added

and candump slcan0 returns SIOCGIFINDEX: No such device. How should I fix this? **NOTE**: Using ubuntu 20.04. **EDIT**: The udev rule properly recognizes the device and runs the script, so the udev rule should work I figure. If I manually set the usb port and run the shell script with sudo ./sclan_add.sh then it also works, displaying the following in tail -f /var/log/syslog

Oct  7 12:53:26 agrirobot slcand: starting on TTY device /dev/ttyUSB0
Oct  7 12:53:26 agrirobot slcand: attached TTY /dev/ttyUSB0 to netdevice slcan0
Oct  7 12:53:26 agrirobot slcand: netdevice slcan0 renamed to slcan0
Oct  7 12:53:26 agrirobot NetworkManager:   [1633604006.8360] manager: (slcan0): new Generic device (/org/freedesktop/NetworkManager/Devices/22)
Oct  7 12:53:26 agrirobot systemd-udevd: ethtool: autonegotiation is unset or enabled, the speed and duplex are not writable.

I can't really see what the problem is with the udev rule calling the shell script, but for some reason this makes the difference.