I don’t have any more ideas unfortunately. Though I’ll add that another user has a similar issue: First time using Linux (ChromeOS) - having problems installing!.
Hopefully the devs see this and have an idea.
Edit: Well, actually… maybe I do have one last idea. ChromeOS with linux enabled seems to be using Debian as its base. Assuming it also packages debians version of anki (and ChromeOS uses an ancient version of debian, debian bullseye to be exact), you should be able to install it like this:
sudo apt install anki
But even if that worked (which it probably doesn’t), that Anki version from bullseye is really ancient.