pi4-devel not available

Thanks for all the work here! 
I'm trying to get your script running on a RPi4 with Ubuntu 21.04 (ARM64). Unfortunatly I'm stuck here:  

>`snap connect pi-fan-ctrl:gpio pi4-devel:bcm-gpio-21`
> error: snap "pi4-devel" is not installed
>`snap install pi4-devel`
> error: snap "pi4-devel" not found

Any idea how to get this connection working?


