REQUIRED: Your webhook should reply 200 OK immediately after receiving webhook, so that WeKan continues working:
https://github.com/wekan/wekan/issues/5077#event-10054506387
https://github.com/wekan/webhook/blob/main/public/index.php#L48C1-L48C1
For receiving webhooks on local network, you could use:
1) Some web form with PHP/Python/other backend, Google search for example code how to receive webhook.
2) NodeRED
4) Java
At Internet you could use for example Zapier.