Yes, sorry for the confusion. I got it working now.
It was my custom transport code which needed updates. See below. I don’t really use PHP that much; I suppose I know just enough to be dangerous. 
Thanks again.
Custom Nextcloud Transport Code (fixed)
<?php
/**
* LibreNMS Nextcloud Talk alerting transport
*
* Copyright (c) 2023 Dan Mahn
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
namespace LibreNMS\Alert\Transport;
use LibreNMS\Alert\Transport;
use LibreNMS\Exceptions\AlertTransportDeliveryException;
class Nextcloudtalk extends Transport
{
protected string $name = 'Nextcloud Talk';
public function deliverAlert(array $alert_data): bool
{
$link = $this->config['nextcloudtalk-link'];
$username = $this->config['nextcloudtalk-username'];
$password = $this->config['nextcloudtalk-password'];
return $this->contactNextcloudtalk($alert_data, $link, $username, $password);
}
public static function contactNextcloudtalk(array $alert_data, $link, $username, $password)
{
$json_data = [
'message' => strip_tags($alert_data['msg']),
];
$json_payload = json_encode($json_data);
$callapi = ['/index.php/call/', '/call/'];
$chatapi = '/ocs/v2.php/apps/spreed/api/v1/chat/';
$url = str_replace($callapi, $chatapi, $link);
// cURL resource ...
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POSTFIELDS, $json_payload);
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type:application/json', 'OCS-APIRequest: true']);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_USERPWD, "$username:$password");
// POST request
$result = curl_exec($ch);
// Get result code
$code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
// ... cURL resource
curl_close($ch);
if ($code != 201) {
$data = [
'title' => 'LibreNMS alert for: ' . $alert_data['hostname'],
'description' => $alert_data['msg'],
];
throw new AlertTransportDeliveryException(
$alert_data,
$code,
'Conversation Token ' . current(array_reverse(explode('/',$url))),
$alert_data['msg'],
$data);
}
return true;
}
public static function configTemplate(): array
{
return [
'config' => [
[
'title' => 'Conversation Link',
'name' => 'nextcloudtalk-link',
'descr' => 'Nextcloud conversation link, e.g. https://cloud.somewhere.tld/call/{token}',
'type' => 'text'
],
[
'title' => 'Username',
'name' => 'nextcloudtalk-username',
'descr' => 'Nextcloud username',
'type' => 'text',
],
[
'title' => 'App Password',
'name' => 'nextcloudtalk-password',
'descr' => 'Nextcloud app password',
'type' => 'password',
],
],
'validation' => [
'nextcloudtalk-link' => 'required|string',
'nextcloudtalk-username' => 'required|string',
'nextcloudtalk-password' => 'required|string',
],
];
}
}
