I'm assuming that the .ova is built on the x86_64 version of Ubuntu, but Arnie can confirm.
It looks like Parallels is starting to support x86_64 VMs on Apple Silicon: https://www.parallels.com/blogs/parallels-desktop-20-2-0/, so you may be able to use this disk image with the latest version of parallels, but don't expect the performance to be great.
Another option for running WeBWorK on a Mac is in a Docker container. There are various different sets of instructions available with differing levels of completeness, so it may take a little bit of experimenting to get set up.