We have a server whose original PKI certificate was issued by a discontinued root CA. We have a replacement certificate issued from a different root authority chain. This site was set up some time ago with Strict-Transport-Security established.
The server key is 4096 bits. The old CA root private key is 1024 bits (it was issued in 2006).
How does one switch PKI keys and certificates for Strict-Transport-Security enabled sites? I have searched for information on this but have so far come up empty.