How did you setup custom domains and SSL for your SaaS?

It varies depending on the project. For static sites/assets I use either Netlify or own VM with CloudFlare in front. Using CF to manage DNS and as resolver on my machines/network make changes immediate.

For the VMs, use certs from Letsencrypt. The renew process is still not fully automated with Nginx and would try Caddy2 next time around.

I don't work with any block storage so nothing for S3 etc.

We've been using CloudFlare's SSL for SaaS [1] offering for the last year, and have nothing but good things to say. You also get the rate limiting and other protections you'd expect from CloudFlare. It's been great not having to worry about CSRs and cert renewals as we've scaled out. Although, we _did_ go down the other day as part of their outage.

[1]https://www.cloudflare.com/ssl-for-saas-providers/

also interested! please share resources if you have any. we have built an implementation using S3. but the bucket name needs to be the same as the domain name.. so not really that scalable..