aura.redirect not working with LWC

Well after doing some research I found out that apparently and according to René Winkelmeyer (Salesforce Principal Developer Evangelist) in this GitHub Issue:

lightning-navigation is currently not a supported experience for Communities.

In Summer '19, Salesforce enhanced the support of lightning-navigation in Community with comm__namedPage (instead of standard__namedPage), pageReferences and state.

https://releasenotes.docs.salesforce.com/en-us/summer19/release-notes/rn_lwc_modules.htm

export default class myClass extends NavigationMixin(LightningElement) {
 //...

 goToFAQCategoryMesInstallations() {
  this[NavigationMixin.Navigate]({
   type: 'comm__namedPage',
   attributes: {
    pageName: 'faq',
   },
   state: {
    'category': 'Mes_installations'
   }
  });
 }
}

this will redirect you to 'yourCommunity'/s/faq?category=Mes_installations

Found the solution (workaround) for this, you can return the url of the PageReference retrieved from Site.login(), then you'll just need to window.open(url, '_self') in the Component's js. As for the PageReference itself it is not a valid type to be returned by AuraEnabled methods.