Simply copy the ar3k folder from the link:
to your system partition /lib/firmware/
Then reboot and it should work.
I have been working on resolving the issue and can happily report that I did at least get rid of the firmware but the driver still needs the sysconfig file (ramps*). I am further working on finding out what it contains and how to remove this too - or to find out more about its content and eventually decide if we can include it in PureOS. So we are making progress on this front too.
Cheers
nicole