Supabase HTTP APIs are no longer using DigiCert as the root CA. This should have no impact on the vast majority of environments, as the other CAs in use are essentially universally trusted.
If your client environment only trusts certificates signed by DigiCert, you could be impacted. We're currently using Cloudflare to serve our HTTP APIs, and recommend ensuring that any client environment that only trusts a specific subset of CAs trusts all of the CAs Cloudflare uses.