We can do Salesforce Messaging For In-App and Web Message Translation in real-time.

lightning:conversationNewMessage can be used to fetch the visitor messages. Using Translation API, we can translate the message and show it to the Agents to assist.

In this Blog Post, I am using Lingvanex for the translation.

Sample Lightning Aura Component:

Component:

<aura:component implements="flexipage:availableForAllPageTypes">   
    <aura:attribute type="String" name="customerMessage"/>
    <aura:attribute type="String" name="translatedMessage"/>
    <aura:handler 
                  event="lightning:conversationNewMessage" 
                  action="{!c.onVisitorMessage}"
                  />
    <lightning:card class="slds-var-p-around_small">
        <b>Customer Message:</b> {!v.customerMessage}
        <br/><br/>
        <b>Translated Message:</b> {!v.translatedMessage}
        <br/><br/>
    </lightning:card>
</aura:component>

JavaScript Controller:

({
    
    onVisitorMessage : function( component, event, helper ) {
        
        let contentMessage = event.getParam(
            'content'
        );
        component.set( 
            "v.customerMessage", 
            contentMessage 
        );
        
        console.log(
            'contentMessage is',
            contentMessage
        );
        
        const options = {
            method: 'POST',
            headers: {
                accept: 'application/json',
                'content-type': 'application/json',
                Authorization: '<AUTHORIZATION_KEY>'
            },
            body: JSON.stringify({
                q: contentMessage, 
                target: 'en'
            })
        };
        
        fetch( 
            'https://api-gl.lingvanex.com/language/translate/v2', 
            options 
        )
        .then( res => res.json() )
        .then( ( res ) => {
            console.log(
                'Result is', 
                JSON.stringify( res )
            );
            const obj = JSON.parse(
            	JSON.stringify( res )
            );
            let tempTranslatedMessage = obj.data.translations[0].translatedText;
            component.set( 
                "v.translatedMessage", 
                tempTranslatedMessage 
            );
        } )
        .catch( ( err ) => {
            console.error( 
                'Error occurred', 
                JSON.stringify( err )
            );
        } );
        
    }
            
})

Trusted URL Configuration:

Add the Translation API URL in the Trusted URLs.

Output: