Hi @Anonymous ,
Short answer Yes. you can. here is what you need to do:
1-Uncheck enable table permission on the entity form , which will allow users to access without authentication (noticed that MSFT will fight you for it and will keep reminding you to keep this enabled)

2-add the entity form on a page

3- click on browse to see the form in the page and fill it without logging in


and the case will be created in Dataverse

HOWEVER, there is a risk that you need to be aware of , Cases will always ask for Contact and Customer (Company) and if you allow unauthenticated customers to fill in this form then you will need to allow them to select their Contact/Company which is a bit tricky as you cant guarantee wrong entry.
Once suggestion, you can create a custom entity that will only take couple text fields and display it on the portal to let customers submit it and extract info from it to create cases in the backend
Let me know if that helps
Thanks
Manar