Concept using Phpseclib to run Rclone from WordPress backend. See https://anchor.host/using-phpseclib-instead-of-disallowed-php-exec/.

rclone-concept.php

<?php
/**
 * Plugin Name:     Rclone Concept
 * Plugin URI:      https://anchor.host/using-phpseclib-instead-of-disallowed-php-exec/
 * Description:     Concept using Phpseclib to run Rclone from WordPress backend.
 * Author:          Austin Ginder
 * Author URI:      https://austinginder.com
 * Text Domain:     rclone-concept
 * Domain Path:     /languages
 * Version:         0.1.0
 *
 * @package         Rclone_Concept
 */

require __DIR__ . '/vendor/autoload.php';
use phpseclib\Net\SSH2;

function run_rclone_command( $command, $username, $password ) {
    $ssh = new SSH2( '127.0.0.1' );
    if ( !$ssh->login( $username, $password ) ) {
       exit( "Login Failed" );
    }
    return $ssh->exec( "cd private/rclone-v*/; ./rclone $command --config rclone.conf" );
 }

// Process ajax events
add_action( 'wp_ajax_rclone_concept_ajax', 'rclone_concept_ajax' );

function rclone_concept_ajax() {
    global $wpdb; // this is how you get access to the database
    // Only proceed if logged in user is an administrator
    if ( ! current_user_can('administrator') ) {
        return true;
        wp_die();
    }
    $request  = (object) $_POST['value'];
    $response = run_rclone_command( $request->command, $request->username, $request->password );
    echo json_encode( $response );
    wp_die(); // this is required to terminate immediately and return a proper response
}

add_action( 'admin_menu', 'rclone_concept_add_admin_menu' );
function rclone_concept_add_admin_menu() { 
    add_options_page( 'Rclone Concept', 'Rclone Concept', 'manage_options', 'rclone_concept', 'rclone_concept_options_page' );
}

function rclone_concept_options_page() { ?>
<script src="https://unpkg.com/qs@6.5.2/dist/qs.js"></script>
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<link href="https://cdn.jsdelivr.net/npm/vuetify@2.2.23/dist/vuetify.css" rel="stylesheet">
<style>
/* WordPress Admin Vuetify Reset */
input[type="color"], input[type="date"], input[type="datetime-local"], input[type="datetime"], input[type="email"], input[type="month"], input[type="number"], input[type="password"], input[type="search"], input[type="tel"], input[type="text"], input[type="time"], input[type="url"], input[type="week"], select, textarea {
    border: 0px;
    background-color: transparent;
}
input[type="checkbox"]:focus, input[type="color"]:focus, input[type="date"]:focus, input[type="datetime-local"]:focus, input[type="datetime"]:focus, input[type="email"]:focus, input[type="month"]:focus, input[type="number"]:focus, input[type="password"]:focus, input[type="radio"]:focus, input[type="search"]:focus, input[type="tel"]:focus, input[type="text"]:focus, input[type="time"]:focus, input[type="url"]:focus, input[type="week"]:focus, select:focus, textarea:focus {
    box-shadow: none;
}
input.readonly, input[readonly], textarea.readonly, textarea[readonly] {
    background-color: transparent;
}
.v-textarea textarea {
    font-size:13px;
    line-height:1.1em;
    font-family:SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace;'
}
</style>
<h2>Rclone Concept</h2>
<div id="app">
    <v-app style="background:transparent;">
    <v-content class="mr-6">
    <v-row>
        <v-col cols="12" md="6">
            <v-text-field label="Rclone Subcommand" v-model="command"></v-text-field>
        </v-col>
        <v-col cols="12" md="3">
            <v-text-field label="SSH Username" v-model="username" type="password"></v-text-field>
       </v-col>
        <v-col cols="12" md="3">
            <v-text-field label="SSH Password" v-model="password" type="password"></v-text-field>
        </v-col>
    </v-row>
    <v-btn color="primary" @click="runCommand()">Run Command</v-btn>
    <v-textarea label="Response" auto-grow solo readonly v-model="response" class="mt-5"></v-textarea>
    </v-content>
    </v-app>
</div>
<script src="https://cdn.jsdelivr.net/npm/vue@2.6.11/dist/vue.js"></script>
<script src="https://cdn.jsdelivr.net/npm/vuetify@2.2.23/dist/vuetify.js"></script>
<script>
new Vue({
  el: '#app',
  vuetify: new Vuetify(),
  data: {
    username: "",
    password: "",
    command: "",
    response: ""
  },
  methods: {
    runCommand() {
        // Prep AJAX request
        var data = {
            'action': 'rclone_concept_ajax',
            'command': "toggle-rclone-remote",
            'value': { 
                'command': this.command,
                'username': this.username,
                'password': this.password,
            }
        }
        // update server
        axios.post( '/wp-admin/admin-ajax.php', Qs.stringify( data ) )
            .then( response => {
                this.command = ""
                this.response = response.data
            })
            .catch(error => {
                console.log(error.response)
            });
    }
  }
})
</script>
<?php

}