For the default URLs generated when you deploy an app, sure, but companies using them commercially are all bringing their own domains (with their own certs).
Nope - having built out the SSL termination stack for a similar company - they are serving millions of commercial sites on their own custom domains with let's encrypt issued certs.
How so?
> Netlify, Vercel, Fly, etc.
For the default URLs generated when you deploy an app, sure, but companies using them commercially are all bringing their own domains (with their own certs).