Question To Anyone Using Authorize.net For Payment

This may be a random question. Specifically asking those that use Authorize.net as their payment option. 

What SSL certificate do you use for your site / domain? My understanding is that in order to use Authorize on any cart platform that we are supposed to use an SSL from DigiCert. I don't know if that's actually valid, and maybe we were just provided false information a while ago. I couldn't find anything that definitely answered this, and when I ask Authorize, they think I am asking something entirely different. I am investigating whether an SSL from Let's Encrypt was possible with this specific combo. 

I don't use that, but I would suspect any SSL will work.