This is what I needed, I put it in /etc/udev/rules.d/80-dolphinbar.rules:
SUBSYSTEM=="hidraw", ATTRS{idVendor}=="057e", ATTRS{idProduct}=="0306", MODE="0666"
I can’t remember where I found this, I’m pretty sure I didn’t figure this out for myself. If you need a DolphinBar, Aliexpress should have you covered. It could be that the vendor code differs for yours, so make sure to watch dmesg when you plug it in.