Hi,
First of all, most domain provider (registrar) will not be providing you a Let's Encrypt certificate, as it's the job of hosting providers.
Since individual or a business can become a hosting provider at any time, there's no way anyone can list all hosting providers who integrate Let's Encrypt with them.
However, there's a list that's on this forum that lists some providers who support Let's Encrypt.
certbot also has a modern list: Does My Hosting Provider Offer HTTPS? | Certbot
Thank you