Hosting a matrix server with synapse, how do you handle registration?

To the people here that host a synapse server, how do you handle registration? Do you use the new matrix authentification server? How does that work? If not, registration works via element web, where you can have a captcha to avoid a bot swarm. However the only accepted captcha in the synapse config is recaptcha. Have you read the news? Well, we will have to change the captcha method. I think I read somewhere it was possible to use hcaptcha on elementweb however the setting does not exist in synapse, or I did not find it. How do we do?