Row Actions can be allowed on Row Selection in Salesforce Lightning Web Component Lightning Data Table using Dynamic Row Actions.

Sample Code:

Apex Class:

Lightning Web Component:

HTML:

<template>      
    <lightning-card title="Accounts" icon-name="custom:custom63">  
        <div class="slds-m-around_medium">  
            <template if:true={accounts}>      
                <lightning-datatable
                    key-field="Id"
                    data={accounts}
                    columns={columns}
                    onrowaction={handleRowAction}
                    onrowselection={handleRowSelection}>
                </lightning-datatable>  
            </template>      
            <template if:true={error}>  
                {error}>                  
            </template>  
        </div>  
    </lightning-card>
</template>

JavaScript:

import { LightningElement, wire } from 'lwc';
import fetchAccounts from '@salesforce/apex/AccountController.fetchAccounts';
import { NavigationMixin } from 'lightning/navigation';

export default class sampleLightningWebComponent extends NavigationMixin( LightningElement ) {
     
    accounts;
    error;
    selectedAccounts = [];
    columns = [   
        { label: 'Name', fieldName: 'Name' },
        { label: 'Industry', fieldName: 'Industry' },
        {
            type: 'action',
            typeAttributes: { rowActions: this.getRowActions.bind( this ) }
        }
    ];

    @wire( fetchAccounts )  
    wiredAccount( { error, data } ) {

        if ( data ) {

            this.accounts = data;
            this.error = undefined;

        } else if ( error ) {

            this.error = error;
            this.accounts = undefined;

        }

    }

    getRowActions( row, doneCallback ) {

        const actions = [];

        if ( this.selectedAccounts && this.selectedAccounts.includes( row[ 'Id' ] ) ) {
            actions.push( {
                'label': 'View',
                'name': 'view'
            } );
            actions.push( {
                'label': 'Edit',
                'name': 'edit'
            } );
        }

        setTimeout( () => {
            doneCallback( actions );
        }, 200 );

    }

    handleRowAction( event ) {

        const actionName = event.detail.action.name;
        const row = event.detail.row;
        switch ( actionName ) {
            case 'view':
                this[ NavigationMixin.Navigate ] ( {
                    type: 'standard__recordPage',
                    attributes: {
                        recordId: row.Id,
                        actionName: 'view'
                    }
                } );
                break;
            case 'edit':
                this[ NavigationMixin.Navigate ] ( {
                    type: 'standard__recordPage',
                    attributes: {
                        recordId: row.Id,
                        objectApiName: 'Account',
                        actionName: 'edit'
                    }
                });
                break;
            default:
        }

    }

    handleRowSelection( event ) {

        const selectedRows = event.detail.selectedRows;

        for ( let i = 0; i < selectedRows.length; i++ ) {

            this.selectedAccounts.push( selectedRows[ i ].Id );

        }

    }

}

JS-meta.xml:

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>57.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__Tab</target>
    </targets>
</LightningComponentBundle>

Output: