Just noticed here another problem. You don’t install things on AppVMs. You should do that on the TemplateVMs on which they are based. Otherwise the applications will disappear when you reboot.
Please read the following docs and it will start to make sense:
edit: The above is wrong. See this comment
This is not specific to Qubes. it’s an issue relating to a missing library. Since you’re doing this via snap I don’t know how to fix it, but it is a similar problem to this one. But there the user was installing natively (not though snap) so finding the appropriate library and installing it should have been easier.